Toward a Sustainability Brand Model: An Integrative Review

: Stakeholder-based brand is increasingly recognized as a measure for corporate sustainability, although the knowledge in this area is relatively unknown. Through a systematic review approach, the present study explores the global knowledge base on sustainability and brand. The most inﬂuential authors and documents are identiﬁed, followed by a discovery of the intellectual structure of the sustainability and brand knowledge base with ﬁve schools of thought. First, the Customer Attitudes and Behavior school refers to behavioral studies (one of the common approaches in sustainability studies). Second, the Tourism Marketing school represents the popular context of sustainability studies that mainly relates to hospitality, destination marketing, and fashion brand management. Third, the Brand Strategy school refers to corporate strategy concerning brand that is widely used to measure corporate sustainability performance such as brand equity. Fourth, the Societal Marketing school provides insights into the marketing strategy that leads a ﬁrm to achieve competitive advantages under concerns about ﬁnite resources and rising environmental and social costs. Finally, the Advanced Quantitative Analysis school reveals an approach that is mainly used when conducting sustainable marketing studies. A model on sustainability brand is then derived, adopting the grounded theory approach. Future research opportunities are also identiﬁed and discussed to continuously advance the scholarship in this speciﬁc area.


Introduction
Competitiveness through tangible practical benefits is no longer viable in today's cut-throat business environment.For this reason, a company's brand-which is viewed as providing both practical and intangible benefits-is essential to its long-term viability.Corporate brand is being valued more and more due to the increasing interest about business sustainability.Given the impact it has on the attitudes and behaviors of consumers, the corporate brand eventually affects the financial performance of the company.It stands for business strength and reputation in the marketplace [1,2].The collective value of a brand or brand equity is a crucial component that describes a company's performance as perceived by its stakeholders [3].It responds to the idea that a company's stakeholders should look at how well the company performs in terms of sustainability and how well its stakeholder-focused strategies and practices work [4].According to research that was carried out in the past [5,6], one of the most critical factors that determines a company's reputation is how its social performance is seen by the public or stakeholders.This increases brand equity.According to Avery and Bergsteiner [7], corporate sustainability should be achieved by building a strong brand and reputation.Similar to this, several studies have discovered that CSR results in brand equity and business reputation and that a positive reputation can result in long-term profitability and consistently higher performance [8].In addition, a corporation can benefit from cause-related activities [9] by enhancing the position of the brand, increasing favorability for the brand, raising the volume of the Sustainability 2023, 15, 5212 2 of 25 revenues, boosting loyalty among customers, and creating strong bonds with alliances and social organizations.
Brand equity, according to Aaker [10], increases the firm's worth through boosting marketing campaigns' efficiency and effectiveness, as well as customer loyalty, prices and profit margins, brand expansion, trade leverage, and competitiveness.Whilst others have claimed that brand equity is determined by the added value that the brand name brings to a product (e.g., [7]), Aaker [10] defines brand equity as a collection of brand assets and liabilities associated with the brand's name and symbol.The value provided by a service or product may be reduced or increased as a result of this grouping.Undoubtedly, a company's perceived reputation should reflect both its past and future actions and, in comparison to its rivals, should reflect the firm's total appeal to all significant stakeholders [11].Additionally, some scholars [12,13] have claimed that brand equity is determined by the overall value that a brand offers to one of its primary goods.The brand equity model includes associations with the brand, a user's impression of the product's quality, and other proprietary aspects of the brand in addition to brand loyalty, brand name awareness, and perceived brand quality [14].Building a powerful brand involves considering all of these aspects as part of the process [15][16][17].
According to empirical research by Winit and Kantabutra [3], companies that want to build their corporate reputation and brand equity implement a stakeholder-focused strategy by recognizing the many different demands of their stakeholders and meeting those needs with pertinent advantages.They especially learn that firms are unable to respond to utilitarian gains since these gains do not directly result in improved relationships with stakeholders; hedonic and eudaimonic happiness are better alternatives because they can increase stakeholders' trust in, loyalty to, and self-identification with the organizations.
By fostering and bolstering stakeholder relationships with firms, the Triple Bottom Line (TBL) outputs-the most often mentioned sustainability performance output-lead to greater brand equity.Bhattacharya et al. [18] claim that contentment, trust, and commitment are the building blocks of a quality relationship.Stakeholder satisfaction, at its most basic level, is an assessment of the company in its entirety based on the experiences of its stakeholders.Stakeholders contrast their overall interactions with the company with the resources they have to provide in order to forge connections with the company.
Stakeholder identification, which is the highest level of relationship quality, is the unification of the self-concept of an individual as well as the concept of a group, which is the group to which an organizational member considers himself or herself belonging to as a member [18].Stakeholders who have a strong level of identification with the company will support it by buying its goods and services, as well as in other ways [19,20], including by assisting it through a crisis.We contend that improved brand equity results from stakeholder relationships of high quality.
To be more specific, stakeholders' faith in corporate brands rises when sustainable firms guarantee their own sustainable welfare [21].The stakeholder model proposed by Winit and Kantabutra [21] suggests that in order to boost brand equity, a company must first earn the trust of its stakeholders by providing them both tangible and intangible advantages.We contend that organizations committed to sustainability opt to provide psychologically beneficial functional benefits, increasing stakeholder trust and brand equity, respectively.According to empirical research, making such an offer is a good strategy to cultivate stakeholder trust and brand equity [21].
In the present study, "sustainability brand" is defined as the aggregate of varied psychological and functional benefits that corporate stakeholders believe they have received from a company via its delivery of sustainability outputs and outcomes.According to the theory of corporate sustainability [22], sustainability outputs are social, environmental, and economic outputs, while sustainability outcomes are sustainable wellbeing as indicated by self-reliance, immunity, and resilience [23].Corporations deliver the sustainability outputs and outcomes by espousing corporate sustainability practices.
Although stakeholders of the company naturally assess corporate reputation and brand equity, these two factors become increasingly significant as corporate sustainability performance measures [4,7] and may be connected to additional significant sustainability performance goals, such as the ability to deliver benefits to the public [24].While corporate sustainability researchers are beginning to acknowledge the significance of organizational brand in guaranteeing business sustainability, there are still many unanswered questions.In the following section, we go over the knowledge gaps and contributions of the current study.

Knowledge Gaps and Research Questions
The knowledge on brand has focused on consumer perception, as brand is traditionally determined by consumer perceptions.However, brand, as well as reputation, as a key sustainability performance outcome, should be determined not by just consumer stakeholders but by a whole range of stakeholders (e.g., [25]).In the literature, very little is known about stakeholder-focused brand, an under-investigated area [21] and the first knowledge gap.
While corporate brand is widely regarded as crucial in the sustainability literature, a definitional confusion exists.For example, green brand and sustainability brand are related terms and share similarities and differences [26].The existing literature provides only some preliminary insights into sustainable branding (e.g., [3,21]), indicating the second knowledge gap for gaining deeper insights into sustainability brand knowledge.
While (a) brand equity, or the collective values of a brand, is essential for corporate sustainability (e.g., [25,27]), (b) brand equity is a useful measure of a company's long-term viability, because each organization's long-term success is contingent on how well its stakeholders' needs are met [28], and (c) building a powerful and green brand in the minds of stakeholders deserves strong investment from organizations [29], little is known about the antecedents of such a brand and its components [30] (the third knowledge gap).
Finally, four views of how to measure brand equity exist in general: finance-based brand equity [31,32]; consumer-based brand equity [14,16,33]; employee-based brand equity [34][35][36]; stakeholder-based brand equity [3,21,25,37].Indeed, the stakeholder-based brand equity is more inclusive than the other three since it encompasses the first three views.However, scanty theoretical, empirical, and conceptual literature about stakeholder-based brand equity is found and is the final knowledge gap.
Due to these knowledge gaps, the primary purpose of this study is to identify the existing brand knowledge through a sustainability lens.It will address the following research questions (RQs): RQ #1: What are the most influential authors and documents regarding sustainability brand?RQ #2: What are the topical foci that researchers are most interested in the sustainability brand knowledge base?RQ #3: What is the intellectual structure of the sustainability brand knowledge base?RQ #4: What are the most popular topics within the sustainability brand knowledge base?RQ #5: What is the most advanced sustainability brand knowledge?
The systematic review begins by identifying the sustainability brand, followed by a research methodology to address the study questions.The outcomes, potential avenues for future research, and study implications are then presented.

Methodology
We adapt the Integrated Systematic Literature Review (ISLR) procedure [38] in the present study, explained step by step here.Following a basic keyword search, a survey is performed to locate the relevant literature on the topic.Next, a bibliometric analysis of the identified literature is performed, followed by the identification of the key findings of the analysis.Following a discussion of the findings, a theoretical framework is developed using the key literature that the bibliometric analysis uncovered.The study is finished by addressing future research opportunities.
Among the review approaches that we employ are Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), bibliometric analysis, and the grounded theory approach.In order to make sense of the literature, a bibliometric analysis is carried out, while PRISMA is utilized to find the pertinent literature on the subject.The creation of the resulting framework is guided by the grounded theory approach, which identifies important bodies of common knowledge.

Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA)
To achieve this study's goal of conducting a thorough systematic literature analysis on sustainability brand, we draw on papers found in the widely-used and respected Scopus database [39].We abide by the PRISMA guidelines [40].
The Scopus database is searched for documents relating to sustainability brand using keywords and then published documents pertaining to sustainability brand are searched for.After that, we search the literature for words that are used frequently."Brand" and "sustainability" are the preliminaries that are utilized as search terms.There are 340 documents found in the Scopus search.
The subsequent screening process allows us to ensure the high quality of the documents.We only accept English peer-reviewed journal articles during the screening process and maintain the inclusion/exclusion standards provided in Table 1 below.Given that we want to review the entire literature on sustainability and brand, the Scopus search timeframe was left undefined, allowing the Scopus search engine to locate all relevant documents regardless of publication date.The first relevant document indexed by Scopus came out in 2010.The search was limited to December 2022, which is when we collected the data.A recent review of sustainability management shows that the literature on sustainability management grew slowly in the 1980s and 1990s, but quickly after 2010.Since 2010, 78% of the Scopus-indexed literature on sustainability management has been published [41].This is also evident in our dataset where we have only one article published in 2010.Thus, it is likely that we have covered the entire literature on sustainability and brand.In the eligibility step, three researchers-including the authors-conduct a fundamental content study to determine the document's admissibility.Each abstract is read to make sure it is pertinent to the goal of the current study.Any disagreements over judgments are settled following a further debate among the three.A total of 53 additional documents are eliminated during the eligibility stage, leaving 287 documents available for further examination (Figure 1).
The primary grounds for rejecting the documents are the absence of author names and unclear source titles.Finally, 287 documents meet the criteria to be peer reviewed and to have the necessary information.The following analyses are performed using these qualified papers.The primary grounds for rejecting the documents are the absence of author names and unclear source titles.Finally, 287 documents meet the criteria to be peer reviewed and to have the necessary information.The following analyses are performed using these qualified papers.

The Bibliometric Analysis
A science map is created and a bibliometric analysis is used to depict the literature's descriptive statistics.We use the VOSviewer version 1.6.18as the primary analysis tool to create a science map.
Science maps, also known as bibliometric maps, can be built to highlight research trends by evaluating citations, co-citations, and the frequency of a phrase, with the nodes representing researchers or keywords, according to Cobo et al. [42] and Van Eck and Waltman [43].
Due to the fact that not all publications report on the whole number of downloads, the current review uses the examination of citations as a proxy for measuring influence, based on the two analysis units of the document and the author [44].
We prefer the co-citation method over the direct citation and bibliographic coupling when it comes to identifying research fronts for a variety of reasons.First, comparatively separate and conceptually congruent research fronts are produced using the co-citation methodology.The objective of the current study is not to extrapolate the similarity of the materials connected to two themes, as is sometimes conducted when using the bibliographic coupling technique [45].Second, the citation is the least reliable strategy [46] among the three.
We choose document and author as the units to gauge brand and sustainability knowledge when utilizing the co-citation analysis approach.Additionally, the co-citation analysis is used to determine how frequently a Scopus database document has referenced

The Bibliometric Analysis
A science map is created and a bibliometric analysis is used to depict the literature's descriptive statistics.We use the VOSviewer version 1.6.18as the primary analysis tool to create a science map.
Science maps, also known as bibliometric maps, can be built to highlight research trends by evaluating citations, co-citations, and the frequency of a phrase, with the nodes representing researchers or keywords, according to Cobo et al. [42] and Van Eck and Waltman [43].
Due to the fact that not all publications report on the whole number of downloads, the current review uses the examination of citations as a proxy for measuring influence, based on the two analysis units of the document and the author [44].
We prefer the co-citation method over the direct citation and bibliographic coupling when it comes to identifying research fronts for a variety of reasons.First, comparatively separate and conceptually congruent research fronts are produced using the co-citation methodology.The objective of the current study is not to extrapolate the similarity of the materials connected to two themes, as is sometimes conducted when using the bibliographic coupling technique [45].Second, the citation is the least reliable strategy [46] among the three.
We choose document and author as the units to gauge brand and sustainability knowledge when utilizing the co-citation analysis approach.Additionally, the co-citation analysis is used to determine how frequently a Scopus database document has referenced another document inside or outside of the same database since it might assess a knowledge base's relational properties and structure [47].
Last but not least, the "research front" and well-liked topics in the knowledge base literature are revealed using the scientific mapping's keyword co-occurrence analysis [46,47].

The Grounded Theory Approach
The process of creating a theory as informed by facts that has been precisely collected and examined is finished with the creation of a theoretical framework [48].We select notable authors and their influential works from a significant school of thought based on the primary domains of knowledge revealed in the earlier bibliometric investigation.The analysis at this final stage is then based on these articles.
The key contribution of this study is that we apply the grounded theory technique, which comprises an interactive process of comparing, contrasting, cataloguing, and categorizing, to extract the most up-to-date knowledge on sustainability brand.Following the reading of each of the discovered documents, the open coding method is applied in order to locate knowledge themes that are consistent across the entirety of each of the documents.These codes are combined into concepts that are thereafter referred to as open codes.Multiple open codes are typically produced by the coding process.With the axial coding approach, the open codes that are closely connected to one another and that overlap with one another are recombined in order to produce aggregated essential notions or core codes.Then, the selective coding process is utilized to pick the focal core code from the core codes.
The primary feature in the current study that naturally emerges from the axial coding process is sustainability; this is the focal core code for the investigation.The focal core code of sustainability is connected to in some way, all other essential codes.In essence, all remaining core codes are influencing concepts.We then trace the history of the focal core code back to its roots in the literature and identify the connections between it and the other core codes.The processed codes and their connections are the state-of-the-art repositories of knowledge from which the relevant framework on sustainability brand is drawn.
Eventually, we also provide suggestions for future research based on our comprehensive systematic review of the literature.

Findings
Our analyses produce the following findings, which respond to the research questions.Beginning with a discussion of the findings of the citation and co-citation analyses, with author and document as the two units of analysis, we provide insights into the knowledge base of the sustainability brand.The outputs from the co-occurrence analysis are presented and discussed after the citation analyses.

Citation and Co-Citation Analyses
To address RQ #1, a series of analyses of citations and co-citations are conducted, with author and document serving as the two units of analysis, as described in greater detail below.

Author Citation and Co-Citation Analyses
The bibliometric evaluation can be employed to identify important authors and documents for knowledge generation [49].To identify scholars, schools of thought, and diverse levels of impact, as well as to rank these scholars according to the quantity of pertinent publications and citations, we use the bibliometric analysis (Table 2).
The top five most cited and the first eighteen scholars in the brand and sustainability literature by total Scopus citations are shown in Table 1.Among them, the top four most productive scholars in this area are Powell, S.M. (4), Gupta, Suraksha (3), Kumar, V. (2), and Lin, J. (2).
The author co-citation analysis (ACA), which visualizes the intellectual structure used by the authors, is used to assess important writers in the literature on brand and sustainability.When two writers are cited jointly in a different publication, this analysis counts as one.According to Bayer et al. [50], this co-citation frequency reveals a degree of effect on the knowledge area both directly and indirectly.Based on the results of an author co-citation analysis presented in Table 3, the top 10 foundation authors in the literature on brands and sustainability are as follows: Interestingly, none of the top ten foundation scholars appear on the list of top-cited authors, indicating that the foundation knowledge in the brand and sustainability literature is not specifically related to sustainability brand.It is not a surprise that Keller is the top co-cited scholar in this area since he is well known as a pioneering scholar in the brand management field.Thus, it makes much sense that a well-known brand management scholar contributes his knowledge to the foundation knowledge of the sustainability and brand literature.However, we need to note that Keller's work focuses almost solely on brand as perceived by customers (known as customer-based brand equity), as opposed to a broad range of stakeholders.This note is also true for all other brand scholars in this author co-citation ranking, such as Sen, Bhattacharya, and Aaker.In addition to the brand management scholars, Fornell and Hair have also contributed to the broad areas of quantitative customer satisfaction measurement and quantitative research methods in general.We can draw from the author co-citation analysis at this point that the specific body of knowledge on sustainability brand is not well established in the literature yet.Scholars have focused their efforts on brand as perceived by customers and still rely to a large extent on the literature from other relevant knowledge bases to inform the development of their studies.
With regard to an examination of the various schools of thought that may be discovered in the brand and sustainability literature, the author co-citation map presents five key clusters, often known as "school of thought", which collectively and cohesively depict the intellectual structure of the brand and sustainability knowledge base (Figure 2), which is the response to RQ #3.
author co-citation ranking, such as Sen, Bhattacharya, and Aaker.In addition to the brand management scholars, Fornell and Hair have also contributed to the broad areas of quantitative customer satisfaction measurement and quantitative research methods in general.We can draw from the author co-citation analysis at this point that the specific body of knowledge on sustainability brand is not well established in the literature yet.Scholars have focused their efforts on brand as perceived by customers and still rely to a large extent on the literature from other relevant knowledge bases to inform the development of their studies.
With regard to an examination of the various schools of thought that may be discovered in the brand and sustainability literature, the author co-citation map presents five key clusters, often known as "school of thought", which collectively and cohesively depict the intellectual structure of the brand and sustainability knowledge base (Figure 2), which is the response to RQ #3.Following are five major schools of thought on the brand and sustainability literature: Brand Strategy (the blue cluster), Advanced Quantitative Analysis in Marketing (the purple cluster), Customer Attitudes and Behavior (the red cluster), Societal Marketing (the yellow cluster), and Tourism Marketing (the green cluster).Each school of thought provides a different perspective on brand and sustainability.The top-three scholars for each school are shown in Table 4 below.Following are five major schools of thought on the brand and sustainability literature: Brand Strategy (the blue cluster), Advanced Quantitative Analysis in Marketing (the purple cluster), Customer Attitudes and Behavior (the red cluster), Societal Marketing (the yellow cluster), and Tourism Marketing (the green cluster).Each school of thought provides a different perspective on brand and sustainability.The top-three scholars for each school are shown in Table 4 below.The first red school of thought, led by Fornell, Han, and Bagozzi, has the most members (37 total) and is the largest.Surprisingly, only Han is found in our Scopus data set as the 11th top-cited scholar, highlighting the value of co-citation analysis, which makes it possible to include cited documents from sources other than Scopus in the analysis.Fornell is well known for his American Customer Satisfaction Index (ACSI), a type of market-based performance measure for firms, industries, economic sectors, and national economies [51].The index employs the econometric approach to estimate the indices, a reason Fornell is often perceived as a scholar in the quantitative research methods knowledge base.Similarly, Bagozzi has contributed to two streams of research.The first one is basic research into human emotions, decision making, social identity, ethics, theory of mind, theory of action, and neuroscience (e.g., [52]), while the other is research into multivariate statistics and its relationship to measurement, construct validity, theory, hypotheses testing, and the philosophy of science (e.g., [53]).Like Fornell, Bagozzi is often perceived as a scholar in the quantitative research methods knowledge base.We determine that Fornell and Bagozzi contribute their knowledge to this cluster on customer attitudes and behavior because the cluster to which they belong is clearly distinct from the other cluster (in purple) that focuses on advanced quantitative analysis.In addition, Han, as the second most co-cited scholar in this school, confirms our conclusion, since he has focused his research on consumer behavior, particularly in the tourism industry.Therefore, it is reasonable to name this school of thought "Customer Attitudes and Behavior".
As the second largest cluster, with 34 scholars, the green cluster is led by Kim, Ko, and Wang.As the leading scholar in this cluster, Kim, as the eighth top co-cited scholar, has contributed to the area of traveler satisfaction and experience.Similarly, Wang has focused his research efforts on hospitality, destination marketing, and branding.In addition, Ko has focused her research efforts on marketing communication and fashion brand management.Fashion has a strong linkage with specific tourism segments such as creative tourism, shopping tourism, and cultural tourism, as it associates with luxury and culture experiences, events, and leisure.Therefore, we name this school of thought "Tourism Marketing".
Led by Keller, Aaker, and de Chernatony, the third largest cluster in blue has 23 scholars.Given that this cluster is exclusively about brand strategy, it is a surprise that none of the three leading scholars are among the top-cited scholars in the brand and sustainability data set.However, Keller, Aaker, and de Chernatony are ranked at 1st, 5th, and 10th in our author co-citation ranking.As the top co-cited scholars, Aaker and Keller have contributed to the area of branding and they are globally known for the brand equity model.While brand equity has later been widely considered a measure for corporate sustainability (e.g., [21,22,54]), the core focus of brand strategy and brand equity are to create competitive point-of-differences and maintain long-term brand values, consistent with long-term orientation of the sustainability concept.One of Keller's studies also found that corporate societal marketing can build brand equity [55].de Chernatony has also focused his research efforts on brand building.Thus, we name this school of thought "Brand Strategy".
The fourth largest school of thought in the yellow cluster comprises 20 scholars, led by Bhattacharya, Sen, and Kotler.Surprisingly, none of them are listed among the top-cited scholars in our brand and sustainability data set.As the fourth and third scholars in the list of top co-cited scholars, Bhattacharya and Sen have focused their research efforts on corporate social responsibility and corporate reputation.They have contributed to the area of the intersection of sustainability and consumer behavior, i.e., when, how, and why consumers and employees respond to companies' sustainability/corporate social responsibility endeavors.As the ninth top co-cited scholar, Kotler is a globally recognized marketing scholar [56] who introduced the strategic marketing for sustainable competitive advantages under the concern about finite resources and the rising of environmental and social costs.In the brand and sustainability literature, Kotler has made contributions to social marketing, demarketing, and brand activism, with the idea that businesses must go beyond corporate social responsibility to address the world's most pressing issues.These sustainability trends in marketing have been implemented across the broad contexts such as business-to-consumers, business-to-business, products, services, and hospitality industries.Thus, we name this school of thought "Societal Marketing".
Finally, the smallest school of thought in the purple cluster comprises seven scholars, led by Hair, Sarstedt, and Ringle.Similarly, none of them appear in the list of top-cited scholars in our dataset.However, Hair, Sarstedt, and Ringle are ranked second, sixth, and seventh, respectively, on our list of top co-cited scholars.All three scholars have contributed to the area of quantitative modeling, particularly structural equation modelling.We can draw from this finding that the literature on brand and sustainability is predominantly quantitative.Therefore, we name this school of thought "Advanced Quantitative Analysis in Marketing".
The proximity of the two schools-Brand Strategy and Advanced Quantitative Analysis in Marketing-shows how closely their respective fields of knowledge are intertwined.On the other hand, there is a large distance between the Tourism Marketing and Societal Marketing schools of thought and the Brand Strategy school of thought, indicating that research conducted by the first two schools is not very much related to brand strategy.Additionally, research in the Brand Strategy school is more closely related to the Customer Attitudes and Behavior school of thought than the two schools of Tourism Marketing and Societal Marketing, which makes much sense since brand is traditionally considered as a perception from customers.Therefore, it can be concluded from the distances among the clusters that the brand and sustainability literature is dominated by quantitative marketing methods and influenced by the literature on customer attitudes and behaviors.

Document Citation and Co-Citation Analyses
The top brand and sustainability articles (Table 5) provide information about the organizational locus of these pieces, which helps to address RQ #2.
The analysis of document citations endorses the existence of three distinct schools of thought: Tourism Marketing, Brand Strategy, and Societal Marketing.Of the top-ten cited documents, three are from the Tourism Marketing school, two from the Societal Marketing school, and one from the Brand Strategy school.The rest do not belong to any of the schools of thought.In terms of quality, out of ten, nine were published by Q1 journal and one by a Q2 journal, suggesting that they are of very high quality.
Then, to investigate papers that have been regularly co-cited, we use document cocitation analysis (Table 6).Publications from our brand and sustainability data set, as well as noteworthy and influential documents not included in the dataset, are included in the final documents.
All the first eleven top documents by co-citations were published with Q1 journals, four of which are from the Journal of Marketing, reflecting the high quality of the foundation literature in the brand and sustainability domain.Five of the documents belong to the Customer Attitudes and Behavior school of thought, four from the Brand Strategy school of thought, and one from the Societal Marketing school of thought, suggesting that the foundation literature in the domain of brand and sustainability is dominated by the literature on customer attitudes and behavior and strategic brand management, which makes much sense since brand is traditionally considered as a perception from consumers.In the sustainability literature, brand equity is considered as a perception from a wide range of stakeholders [21].That is possibly the reason one document is from the Societal Marketing school of thought.Notably, there is no document commonly identified by both citation and co-citation analyses.

Co-Occurrence Analysis
In order to provide support for the earlier citation studies and to provide an answer to RQ #4, we use the co-occurrence analysis method.According to Zupic and Cater [47], this is accomplished by adding subject specializations to the brand and sustainability studies.The author keyword co-occurrence search is configured with a threshold of five keyword occurrences.The selection of author keywords is justified by the fact that, given the study topic, authors are best positioned to say whether their works are connected to brand and sustainability.
A total of 28 out of the 1129 keywords satisfy the requirement (see Table 7).Figure 2 shows a co-word map that demonstrates the relative weighting of various different words connected to brand and sustainability.A connecting line that represents a link strength has a thickness between keyword nodes that denotes the existence of a relationship between those nodes.The first ten frequently appearing keywords in the review dataset show that these terms are pertinent and of interest to brand and sustainability scholars, as shown in Table 7. Sustainability, along with words containing the word "brand", is the word that appears the most frequently in the literature and has the strongest link to it.
Therefore, according to major node sizes, the document co-occurrence science map (Figure 3) shows seven clusters of topical focuses.The topical focus for the red cluster is "brand", whereas the topical focus for the green cluster is "brand image".While brand loyalty is the topical focus of the yellow cluster, "customer behavior" is the topical focus of the dark blue cluster.While brand equity is the topical focus for the light blue cluster, "sustainability" is the topical focus for the purple cluster.The orange cluster also identifies the topical focus as "business social responsibility".
"brand", whereas the topical focus for the green cluster is "brand image".While brand loyalty is the topical focus of the yellow cluster, "customer behavior" is the topical focus of the dark blue cluster.While brand equity is the topical focus for the light blue cluster, "sustainability" is the topical focus for the purple cluster.The orange cluster also identifies the topical focus as "business social responsibility".Because the literature is always evolving, especially following the introduction of new knowledge, scholars are quick to respond to shifts in the environment.According to Boyack and Klavans [46] and Zupic and Cater [47], the "research front" of the knowledge base literature can be determined using scientific mapping.We depict science mapping in this work to explain the research frontiers and the most interesting topics among scholars (See Figure 4).Given that the average year these keywords were published is earlier than 2018, the overlay virtualization map (Figure 4) suggests that the majority of them are very recent.Sustainability, branding, brand management, and brand experience are some of them.Between late 2018 and early 2019, more fresh research on CSR and green marketing was conducted.Mid-2019 to early-2020 marks the beginning of brand, brand loyalty, and brand image study.Most recently, research on brand equity and buying intention has started as of mid-2020.Because the literature is always evolving, especially following the introduction of new knowledge, scholars are quick to respond to shifts in the environment.According to Boyack and Klavans [46] and Zupic and Cater [47], the "research front" of the knowledge base literature can be determined using scientific mapping.We depict science mapping in this work to explain the research frontiers and the most interesting topics among scholars (See Figure 4).Given that the average year these keywords were published is earlier than 2018, the overlay virtualization map (Figure 4) suggests that the majority of them are very recent.Sustainability, branding, brand management, and brand experience are some of them.Between late 2018 and early 2019, more fresh research on CSR and green marketing was conducted.Mid-2019 to early-2020 marks the beginning of brand, brand loyalty, and brand image study.Most recently, research on brand equity and buying intention has started as of mid-2020.

Cutting-Edge Knowledge on Sustainability Brand
To answer RQ #5, the grounded theory process begins by identifying scholars and relevant documents for analysis.Based on the two lists of top author citation and co-citation analyses in the knowledge domain of brand and sustainability above, we cannot identify the most influential scholars because no scholar appears on both lists (e.g., [38,76]).Therefore, we closely examine scholars who belong to the five schools of thought.The only school where scholars produced research work directly on sustainability brand is the Brand Strategy school, while scholars who belong to the other four schools of Customer Attitudes and Behavior, Tourism Marketing, Societal Marketing, and Advanced Quantitative Analysis in Marketing have not focused their research efforts specifically on sustainability brand.
The next step is to determine influential scholars in the Brand Strategy school who appear in both rankings of author citation and co-citation analyses, because they are the most influential scholars in the specific knowledge domain of sustainability brand.Only three of the top ten researchers from the author co-citation analysis appear on both lists, as seen in Table 8 below.We call them top sustainability brand scholars as they have specifically produced knowledge in this niche area.

Cutting-Edge Knowledge on Sustainability Brand
To answer RQ #5, the grounded theory process begins by identifying scholars and relevant documents for analysis.Based on the two lists of top author citation and cocitation analyses in the knowledge domain of brand and sustainability above, we cannot identify the most influential scholars because no scholar appears on both lists (e.g., [38,76]).Therefore, we closely examine scholars who belong to the five schools of thought.The only school where scholars produced research work directly on sustainability brand is the Brand Strategy school, while scholars who belong to the other four schools of Customer Attitudes and Behavior, Tourism Marketing, Societal Marketing, and Advanced Quantitative Analysis in Marketing have not focused their research efforts specifically on sustainability brand.
The next step is to determine influential scholars in the Brand Strategy school who appear in both rankings of author citation and co-citation analyses, because they are the most influential scholars in the specific knowledge domain of sustainability brand.Only three of the top ten researchers from the author co-citation analysis appear on both lists, as seen in Table 8 below.We call them top sustainability brand scholars as they have specifically produced knowledge in this niche area.
The top three identified scholars and their documents are shown in Table 8.They are Gupta, Kumar, and Kantabutra, respectively.Looking more closely in details, it turns out that there are two scholars with the name "Gupta, S.": Gupta, Suraksha and Gupta, Shuchi.Therefore, there are essentially four top scholars in this specific knowledge domain of sustainability brand as shown in Table 8.Consistently, Gupta, Suraksha is also identified as number two on the ranking of top-cited scholar in the brand and sustainability literature.Based on the list of the eight documents from the most influential scholars on sustainability brand (Table 9), two were published in Q2 and Q3 journals and the rest were in Q1 journals, reflecting a high quality of the work in this specific domain.As these eight documents appear in both document citation and co-citation analyses, they become the most influential documents in the sustainability brand knowledge base.We start our coding process by reading all the eight documents and then analyze them, following the grounded theory approach.We only focus our reading on the sections of introduction, the background literature, discussion of findings, future research directions, and conclusions.The methodology section of each document is excluded from the coding process.Once we have collected the documents or data, we use the grounded theory's [83] coding process, which is shown in Figure 5, to analyze and combine the data.Once we have collected the documents or data, we use the grounded theory's [83] coding process, which is shown in Figure 5, to analyze and combine the data.First, the open-coding method is used to find themes in the collected documents or data.This is carried out by analyzing the documents line by line and paragraph by paragraph [84].Later, the researchers put these codes together to form ideas, which we later called "open codes".When open coding is used, there are many open codes [48,83].The next step in the axial coding process is for the researchers to recombine closely linked and overlapping open codes into aggregated key concepts or core codes.Then, the researchers choose the main core code from among the core codes.This is called the selective coding process [84].
From the coding process, the following nine themes emerge: corporate sustainability, organizational culture, sustainability practice, stakeholder benefits, brand communication, brand knowledge and differentiation value, sustainability behavior, stakeholder relationship, and brand equity.Among them, sustainability clearly emerges as the focal core code; the rest are influential core codes.To develop a model, we explore the relationships among them.At times, we supplement our arguments with other relevant documents from the identified scholars to enhance our understanding about the relationships.
The documents from Gupta, Suraksa and Kumar, V. [58] emphasize the role of brand knowledge and value via corporate culture in enhancing corporate sustainability performance.Along with Kantabutra and his colleagues [21,82], Gupta, Suraksa and Kumar, V.
[58] also point out the importance of sustainability practice in developing and nurturing a brand and vice versa, as Gupta, Suraksa and Kumar, V. [58] suggest that a company's ability to push opportunities available to it for greater performance, when viewed as a sustainability practice, can be strengthened by its brand.It is these sustainability practices that directly deliver benefits to a whole range of stakeholders, which is another emerging theme.
The next emerging theme from the documents is brand communication.All scholars recognize the critical role of brand communication internally in the organization and externally among outsider stakeholders.Kumar V. and his colleagues [58,69] suggest that organizations can focus internal branding by communicating with all stakeholders to cocreate brand congruence.The documents from Gupta, Shuchi totally focus on CSR communication via social media to develop a brand via brand admiration.Another emerging theme related to brand communication is brand knowledge and differentiation value as perceived by stakeholders who have received benefits from the corporation.It is the brand knowledge that helps stakeholders to differentiate the values delivered by different corporations.Gupta, Suraksha, and his colleagues emphasize the stakeholder-perceived brand knowledge and differentiation value, while Kantabutra and his colleagues indirectly point out the role of brand knowledge and differentiation value as perceived by stakeholders in creating brand equity.In supporting the stakeholder-brand equity relationship, Suraksha Gupta, Kumar, V., Gupta, Shuchi and Kantabutra, S. commonly address brand perception by stakeholders.Brand perception by stakeholders comes in many forms such as customer equity (Suraksha Gupta) and brand identity (Kumar, V.), brand First, the open-coding method is used to find themes in the collected documents or data.This is carried out by analyzing the documents line by line and paragraph by paragraph [84].Later, the researchers put these codes together to form ideas, which we later called "open codes".When open coding is used, there are many open codes [48,83].The next step in the axial coding process is for the researchers to recombine closely linked and overlapping open codes into aggregated key concepts or core codes.Then, the researchers choose the main core code from among the core codes.This is called the selective coding process [84].
From the coding process, the following nine themes emerge: corporate sustainability, organizational culture, sustainability practice, stakeholder benefits, brand communication, brand knowledge and differentiation value, sustainability behavior, stakeholder relationship, and brand equity.Among them, sustainability clearly emerges as the focal core code; the rest are influential core codes.To develop a model, we explore the relationships among them.At times, we supplement our arguments with other relevant documents from the identified scholars to enhance our understanding about the relationships.
The documents from Gupta, Suraksa and Kumar, V. [58] emphasize the role of brand knowledge and value via corporate culture in enhancing corporate sustainability performance.Along with Kantabutra and his colleagues [21,82], Gupta, Suraksa and Kumar, V. [58] also point out the importance of sustainability practice in developing and nurturing a brand and vice versa, as Gupta, Suraksa and Kumar, V. [58] suggest that a company's ability to push opportunities available to it for greater performance, when viewed as a sustainability practice, can be strengthened by its brand.It is these sustainability practices that directly deliver benefits to a whole range of stakeholders, which is another emerging theme.
The next emerging theme from the documents is brand communication.All scholars recognize the critical role of brand communication internally in the organization and externally among outsider stakeholders.Kumar V. and his colleagues [58,69] suggest that organizations can focus internal branding by communicating with all stakeholders to co-create brand congruence.The documents from Gupta, Shuchi totally focus on CSR communication via social media to develop a brand via brand admiration.Another emerging theme related to brand communication is brand knowledge and differentiation value as perceived by stakeholders who have received benefits from the corporation.It is the brand knowledge that helps stakeholders to differentiate the values delivered by different corporations.Gupta, Suraksha, and his colleagues emphasize the stakeholder-perceived brand knowledge and differentiation value, while Kantabutra and his colleagues indirectly point out the role of brand knowledge and differentiation value as perceived by stakeholders in creating brand equity.In supporting the stakeholder-brand equity relationship, Suraksha Gupta, Kumar, V., Gupta, Shuchi and Kantabutra, S. commonly address brand perception by stakeholders.Brand perception by stakeholders comes in many forms such as customer equity (Suraksha Gupta) and brand identity (Kumar, V.), brand admiration, consumer purchase intention, loyalty and purchase likelihood (Gupta, Shuchi), and stakeholder trust and psychological benefits (Kantabutra).It is regarded as the result of corporate activities/practices with stakeholders.
Once stakeholders perceive that they receive brand knowledge and differentiation value of the corporation, they behave sustainably.This sustainability behavior includes adopting sustainability behaviors, co-operating with stakeholders, and purchase intention among consumers.It is this sustainability behavior that leads to forging the strong relationship between stakeholders and the benefits-delivering corporation.Stakeholder relationship, as the next emerging theme, emerges as all scholars address developing and maintaining the corporate relationship with stakeholders.Kantabutra and his colleagues and Kumar, V. suggest various forms of stakeholder relationships, including stakeholder participation and collaboration and customer relationship.
Brand equity, the overall value added to a core product or the incremental utility as a result of its brand name [85], is the next emergent theme that emerges from the documents that Kantabutra and his colleagues have produced over the years.They suggest that brand equity can be developed and maintained through sustainability practices and the resulting stakeholder relationship can be developed and enhanced by delivering different types of benefits to stakeholders.All of the cited researchers either directly or indirectly discuss brand equity, because (a) brand co-creation is the process of intentional engagement between or among two or more parties that influences a brand [86] and (b) brand equity is determined by stakeholders' assessments of the brand's worth [87].More and more research (e.g., [7,22]) claims that brand equity results in corporate sustainability.
After determining the relationships among the themes, the following model in Figure 6 as the cutting-edge knowledge on sustainability brand is derived.admiration, consumer purchase intention, loyalty and purchase likelihood (Gupta, Shuchi), and stakeholder trust and psychological benefits (Kantabutra).It is regarded as the result of corporate activities/practices with stakeholders.
Once stakeholders perceive that they receive brand knowledge and differentiation value of the corporation, they behave sustainably.This sustainability behavior includes adopting sustainability behaviors, co-operating with stakeholders, and purchase intention among consumers.It is this sustainability behavior that leads to forging the strong relationship between stakeholders and the benefits-delivering corporation.Stakeholder relationship, as the next emerging theme, emerges as all scholars address developing and maintaining the corporate relationship with stakeholders.Kantabutra and his colleagues and Kumar, V. suggest various forms of stakeholder relationships, including stakeholder participation and collaboration and customer relationship.
Brand equity, the overall value added to a core product or the incremental utility as a result of its brand name [85], is the next emergent theme that emerges from the documents that Kantabutra and his colleagues have produced over the years.They suggest that brand equity can be developed and maintained through sustainability practices and the resulting stakeholder relationship can be developed and enhanced by delivering different types of benefits to stakeholders.All of the cited researchers either directly or indirectly discuss brand equity, because (a) brand co-creation is the process of intentional engagement between or among two or more parties that influences a brand [86] and (b) brand equity is determined by stakeholders' assessments of the brand's worth [87].More and more research (e.g., [7,22]) claims that brand equity results in corporate sustainability.
After determining the relationships among the themes, the following model in Figure 6 as the cutting-edge knowledge on sustainability brand is derived.From left to right, the model starts from an organizational culture in which stakeholder focus is a core value, among other sustainability values.This culture leads to the formation of the stakeholder-focus sustainability practices such as green initiatives, cleaner production, reversed logistics, and social responsible activities.Clearly, these practices deliver physical and emotional benefits to a broad range of stakeholders, leading stakeholders to perceive the value and knowledge of the brand.Sustainability practice From left to right, the model starts from an organizational culture in which stakeholder focus is a core value, among other sustainability values.This culture leads to the formation of the stakeholder-focus sustainability practices such as green initiatives, cleaner production, reversed logistics, and social responsible activities.Clearly, these practices deliver physical and emotional benefits to a broad range of stakeholders, leading stakeholders to perceive the value and knowledge of the brand.Sustainability practice information also spreads out to relevant stakeholders via internal and external brand communication strategy, allowing stakeholders to receive messages, which then leads to perceived brand knowledge and differentiation value.Perceived brand knowledge and differentiation value lead to creating and nurturing sustainability behavior among stakeholders, including consumer product adoption and purchase intention and stakeholder cooperation.Sustainability behavior among stakeholders leads to forging a trusted stakeholder relationship.Over time, building long-term trustworthy relationships with a variety of stakeholders can boost brand equity, which in turn can affect company sustainability.

Overall Discussions of the Findings
In the above analysis sections, we have provided specific discussions related to findings from each analysis.In this section, we portray the landscape of the sustainability brand knowledge base by highlighting the overall findings from our review above and future directions for sustainability brand research drawn from the study.
From a bird's eye view, our review results indicate that the sustainability and brand knowledge base is heavily dominated by the consumer-focus perspective, as opposed to the stakeholder-focus perspective.This is consistent with the view of corporate sustainability research in that the short-term maximization of profitability still prevails in the corporate world [23], although more and more businesses are increasingly aware of the need to balance among the three domains of sustainable development [88], the Triple Bottom Line results.Our review results also indicate the scanty knowledge on sustainability brand, pending future research into what characterizes a sustainability brand and how to develop one.In particularly, increasingly brand equity is suggested by corporate sustainability scholars as a proxy of corporate sustainability (e.g., [54,58,89]).
Our author citation and co-citation analyses endorse our conclusion above.Based on the list of the top-cited scholars, most of them only published one or two articles with brand and sustainability in their content.In particular, the five top-cited authors in the list co-authored only one same article [57].This indicates the critical lack of interest in brand and sustainability research since brand equity is increasingly considered as a proxy for corporate sustainability in the literature (e.g., [54,58,89]) and we know so little about it.
In terms of author co-citation analysis, the results indicate that all top co-cited authors on the list have contributed their knowledge about consumer-based brand and quantitative research methods to the foundation of the sustainability and brand knowledge base.None of the top co-cited authors on the list are known specially on sustainability brand.This suggests that the sustainability and brand literature is predominantly consumer-focused and quantitative, which is understandable since brand is traditionally considered as commonly perceived by consumers [68] and consumer research by nature is traditionally quantitative.The co-citation analysis also reveals that none of the top ten co-cited scholars contribute to the area of sustainability since they do not appear on the list of top cited scholars.Thus, future research into brand should take into consideration perceptions from a wide range of stakeholders.
Drawing upon the author co-citation analysis, the resulting schools of thought in the sustainability and brand knowledge base confirms the lack of the literature specifically on sustainability brand.The only school of thought among the five in this knowledge base is the Brand Strategy school led by Keller, Aaker, and de Chernatony, with only 23 scholars.All leading scholars in this school are brand scholars, but they look at brand from the consumer point of view as opposed to that of stakeholders, indicating future research directions.
Based upon the document citation and co-citation analyses, we can conclude that the knowledge base on brand and sustainability is of good quality, as the scholars published research on sustainability and brand in high-quality journals and this knowledge base is built upon published knowledge in high-quality journals as the foundation.Similarly, we can also draw from the document citation and co-citation analyses that scholars in this knowledge domain of sustainability and brand are interested in the broad sphere of tourism marketing, societal marketing, and brand strategy.The document co-citation analysis also confirms our earlier conclusion that scholars in the knowledge domain are interested in the customer-focus perspective of brand and sustainability, since most of the top co-cited documents are about customer attributes and behaviors and brand strategy from the customer perspective.However, the document co-citation analysis confirms that there is an interest among scholars on brand and society, since there is one top co-cited document on societal marketing, suggesting that scholars are starting to consider the intersection between brand and society.
Informed by the word-co-occurrence analysis, we can conclude that sustainability is a prominent key word in this knowledge base on sustainability and brand, as "sustainability", along with words containing the word "brand", is the word that appears the most frequently in the literature.Certainly, we can draw from the word co-occurrence that sustainability brand is a promising area for future research since the research trend has moved forward in this direction.Sustainability, branding, brand management, and brand experience are some of the recent keywords from this analysis.We can also determine that brand scholars have increasingly associated brand with sustainability since late 2018, when words such as CSR and green marketing started to appear.Most recently, brand equity has become prominent since mid-2020, possibly because brand is widely considered as a proxy for corporate sustainability in the sustainability literature (e.g., [54,58,89]).
Finally, our grounded theory process (used to analyze and synthesize the identified documents that are directly related to sustainability brand) reveals cutting-edge knowledge on sustainability brand.We have identified some antecedents to sustainability brand and relationships among them, which eventually lead to improving the prospect of corporate sustainability via the sustainability brand model.Certainly, future research can examine and/or explore the causal relationships among them and continuously refine the model, in response to a call by Winit and Kantabutra [21].

Future Research Directions
We summarize directions for future research in this section.Clearly, brand scholars should take into consideration a whole range of stakeholders in their future research, as opposed to consumer stakeholders alone.Future study can also quantitatively analyze the connections between the sustainability brand model's elements in various organizational and industrial contexts.One can examine whether the antecedent constructs lead to improving corporate sustainability via brand equity.
Future research can also qualitatively explore how the eight constructs help to improve the prospect of corporate sustainability, the results of which can help to refine the theory of corporate sustainability [22].
More specifically, the literature in the past has extensively investigated brand equity from different angles such as consumer-based brand equity [31], employer-based and employee-based brand equity [90], industrial brand equity [91], global brand equity [92], and social brand equity [93].The sustainability literature has time and again endorsed the important role of sustainability practices that could lead to creating stronger brand equity.Future studies, therefore, should deliberately focus on synthesizing dimensions of sustainability brand equity and investigating the relationship between the dimensions and sustainability outcomes.
Over time, collective findings can help to enhance our understanding about the sustainability brand model and how brand equity can be used as a proxy for corporate sustainability.

Conclusions
Through the systematic review approach, the present review has provided the answers to the five research questions.First, we identify the most influential authors and documents regarding sustainability brand.The top four influential scholars in the specific sustainability brand knowledge base are: Gupta, Suraksha; Gupta, Shuchi; Kumar; Kantabutra.Accordingly, their eight documents are the most influential documents in this specific knowledge domain.

Figure 2 .
Figure 2. Author co citation analysis of brand and sustainability, 2010-December 2022.

Figure 3 .
Figure 3. Map of word co-occurrences in the brand and sustainability literature from 2010 to December 2022

Figure 3 .
Figure 3. Map of word co-occurrences in the brand and sustainability literature from 2010 to December 2022.

Figure 4 .
Figure 4. Map of the brand and sustainability literature organized by recency and term co-occurrence, 2010-December 2022.

Figure 4 .
Figure 4. Map of the brand and sustainability literature organized by recency and term co-occurrence, 2010-December 2022.

Table 1 .
Criteria for literature inclusion and exclusion.

Table 2 .
The top 5 authors of brand and sustainability, ranked by citations, from 2010 to December 2022.

Table 3 .
The top ten authors of brand and sustainability literature from 2010 to December 2022, in order of co-citations.

Table 4 .
Top three scholars by school of thought, 2010-December 2022.

Table 5 .
The top ten documents on brand and sustainability, ranked by citations, from 2010 to December 2022.

Table 6 .
The first 12 documents in the brand and sustainability literature, in order of co-citations, from 2010 to December 2022.

Table 7 .
The top ten keywords in the brand and sustainability literature, ranked by co-occurrence, from 2010 to December 2022.

Table 8 .
The top ten brand strategy scholars from 2010 to December 2022, in order of author cocitations.

Table 8 .
The top ten brand strategy scholars from 2010 to December 2022, in order of author co-citations.

Table 9 .
The most influential scholars on sustainability brand from 2010 to December 2022 and their documents, in order of citations and co-citations.