A Review of the Literature about Sustainability in the Work of the Future: An Overview of Industry 4.0 and Human Resources

: Background: Industry 4.0 presents a volatile environment and is attentive to the need for changes in employees’ behavior. This paper aimed to investigate academic trends relating to the themes of Industry 4.0 (I4.0) and human resources (HR). Methods: a total of 354 articles on the thematic area published in the Scopus database between 2014 and 2023 were analyzed. Results: Industry 4.0 is related to various themes connected to the productive environment, with a focus on technology. Over time, topics related to human resources management have become integrated into research on Industry 4.0. In this scenario, research demonstrates the importance of studies on workers’ education and training. The ﬁndings presented in this paper are relevant for researchers, academics, and managers, serving as a guide for future research on I4.0. The main contribution is facilitating the analysis of the role of workers in the Industry 4.0 scenario for different professionals, such as researchers, teachers, and HR managers. Conclusions: the present study points out new possibilities for research on Industry 4.0 and HR. These possibilities should guide researchers and professionals in their implementation.


Introduction
Industry 4.0 (I4.0) is a phenomenon that pays particular attention to the organization's constant need for changes in employees' attitudes, behaviors, and mindsets toward their own volatile environment [1]. Industry 4.0 has been defined by German Trade and Invest (Gesellschaft für Außenwirtschaft und Standortmarketing GmbH (GTAI)) [2] as "the technological evolution from embedded systems to cyber-physical systems that enable technologies, such as the Internet of Things (IoT) and online data and services, to create a truly networked world in which intelligent objects communicate and interact with each other". The concept of I4.0 includes a high degree of application of automation and digitalization technologies [3] and encompasses a variety of technological solutions [4].
In these specific environments, Gackowiec et al. [4] identified the interaction of work environment variables (storage, natural hazards, and ventilation problems), machinery (becoming more advanced from the information technology point of view), and finally, the human factor as key performance indicators (KPI).
Developed countries are already experiencing far-reaching transformations in their factory environments caused by I4.0 developments [1].
The transformations are related to the manufacturing environment and the impact on the nature of work structures, such as human resources management (HRM) [1], the new skills required for future industrial and managerial workers, the job structure [5], and different approaches within the educational process [3].
According to Al Amiri and Shawali [6], strategic talent management (or HR) is a fundamental driver for shaping values and beliefs in any organization.
The advanced technology that characterizes one of the main elements of I4.0 plays a key role in maximizing productivity and increasing wealth creation. However, this technology has been significantly altering the way work is undertaken, as well as changing the role of HR within the organization [1], according to external changes in the skills demanded of workers because of digitalization [3]. Marinas,Dinu,Socol,and Socol [7] analyzed the Romanian case of transition in the European manufacturing sector toward Industry 4.0 digital technologies. The authors indicate that one of the effects of Industry 4.0 is an increase in the demand for human resources skills.
Such is the relevance of the topic that Grencikova, Kordos, and Berkovic [8] specifically address the effects of implementing the concept of Industry 4.0 on the development of labor productivity in the business sector of Slovakia, as well as on job creation and job displacement.
Vrchota et al. [9] analyzed the implications of Industry 4.0-related production changes on workers in the Czech Republic, describing the HR prerequisites for successful implementation of I4.0 in the country. Nedelko [10] conducted a study with 222 employees working in organizations across Europe based on management tools for organizational work in Industry 4.0 environments. The author explored the main organizational and personal drivers for using management tools. It was revealed that the use of certain strategies was higher among individuals with a higher educational level.
Al Amiri and Shawali [6] explored the procedures, policies, and talent management practices in the departments of a public hospital in the United Arab Emirates, investigating the skills, competencies, and programs required for these departments in the context of Industry 4.0.
The World Economic Forum [11] lists the key competencies required for workers in Industry 4.0, which are (i) the development of leadership skills, (ii) management of the integration of technology with the worker, (iii) enhancement of worker experience as an employee, (iv) building a learning culture that is fast paced and yet personalized, (v) metrics for worker appreciation, and (vi) embedding of diversity and inclusion in factories.
Jerman et al. [12] proposed a worker competency model based on six groups of competencies form the key competencies of I4.0 workers: (i) Technical skills include technical knowledge, such as knowledge of technologies, mechanical engineering, electronics, and computer science (such as programming), openness to changes, flexibility, curiosity, critical and analytical thinking, and multilingualism; (ii) Innovation and creativity, which require flexibility and openness to receive a higher level of education, flexible responses, openness and flexibility in problem solving; (iii) Openness to learning includes cooperation with robots and technological literacy and continuous information flow and exchange between humans and machines; (iv) Flexibility and adaptation to change refers to the future and how it may lead to a restructuring of jobs; employees will need to adapt to new technology; (v) Soft skills, as smart technology alone does not guarantee competitiveness; some of the soft skills include multilingualism, leadership, motivation and understanding, and environmental awareness; (vi) Information and communication technology (ICT) skills or literacy, which is reflected in the fact that there will be an increase in machine operator, software maintenance, and hardware maintenance jobs in the future.
Similarly, Blayone and Van Oostveen [14] suggest a set of five skill dimensions for Industry 4.0, which are technological, flexibility, inter-agent, interpersonal, and innovation.
Kipper et al. [15] emphasize that the relationship between universities, industry, and governments forms the "triple helix" competences: technologies, knowledge, and skills, as shown in Figure 1. (vi) Information and communication technology (ICT) skills or literacy, which is reflected in the fact that there will be an increase in machine operator, software maintenance, and hardware maintenance jobs in the future.
Similarly, Blayone and Van Oostveen [14] suggest a set of five skill dimensions for Industry 4.0, which are technological, flexibility, inter-agent, interpersonal, and innovation.
Kipper et al. [15] emphasize that the relationship between universities, industry, and governments forms the "triple helix" competences: technologies, knowledge, and skills, as shown in Figure 1. On a different note, Fareri et al. [16] estimated the effects of Industry 4.0 on job roles and competences using text mining. The authors mention three important groups of competencies: (i) everyday execution skills, (ii) operational skills, and (iii) functional skills.
Understanding the key competencies required by I4.0 is important because the way HR acts in recruiting and selecting employees is based on these factors.
After this brief introduction, the goal of the present study is to identify the research trends relating to the themes of Industry 4.0 and human resources.
The three following sub-questions will guide our research: (1) What are the developments and trends in Industry 4.0 and human resources research? On a different note, Fareri et al. [16] estimated the effects of Industry 4.0 on job roles and competences using text mining. The authors mention three important groups of competencies: (i) everyday execution skills, (ii) operational skills, and (iii) functional skills.
Understanding the key competencies required by I4.0 is important because the way HR acts in recruiting and selecting employees is based on these factors.
After this brief introduction, the goal of the present study is to identify the research trends relating to the themes of Industry 4.0 and human resources.
The three following sub-questions will guide our research: (1) What are the developments and trends in Industry 4.0 and human resources research?
(2) Who are the prolific scholars, affiliations, and social networks on Industry 4.0 and human resources, and where are they situated? (3) What is the main thematic focus of the Industry 4.0 study and human resources application fields? This paper aims to investigate academic trends relating to the themes of Industry 4.0 (I4.0) and human resources (HR). Meeting this objective is important to help researchers, professors, corporate trainers, human resource managers, policymakers, and system designers to analyze the role of workers within the Industry 4.0 scenario more effectively.

Materials and Methods
A systematic literature review was conducted to examine scientific production pertaining to the subject of Industry 4.0 and human resources available in the Scopus database until 2023.
This database was selected as it is one of the largest, with 25,990 journals [17]. Furthermore, the Scopus database was reported to produce a greater number of publications on this subject, thus justifying its use.
A Scopus database search was undertaken on 1 August 2023. Moreover, the search was restricted to original articles and review articles. Original articles are constructed based on original topics or approaches. On the other hand, review articles analyze and discuss previously published information, often employing specific methodologies such as PRISMA and Ordinatio, enabling us to stay abreast of the latest advancements in a specific field [18,19]. The search strategies employed are shown in Table 1.  For the bibliometric analysis, the 354 documents in the research corpus were exported to a BibTex file. All documents were considered in the analysis. The bibliometric analyses were performed using the Biblioshiny graphical interface of the R-Studio software's Bibliometrix package, an open-source application that consists of multiple tools that facilitate the conduction of quantitative bibliometric research, including the main algorithms for statistical analysis and scientific mapping, as demonstrated by Agbo et al. [20]. The Bibliometrix package for R-Studio creates results that take the metadata registered in the Scopus database into account (author keywords, which represent the author's main research area or areas; abstracts; keywords described in the published paper; author affiliations and the content within portable document format (PDF) documents). Table 2 displays the information extracted from the Scopus database using the BibTex format. Table 3 shows the categories based on which the data analysis was performed using the Bibliometrix package for R-Studio. The findings shall be presented in the next section.

Results
This section provides the results and discussion of the discoveries to illustrate (i) the advancement and trends of research in HR and I4.0 concerning publication output, location, and sources, (ii) prolific scholars, affiliations, and social networks, and (iii) the thematic emphasis of the HR and I4.0 domain. Table 4 describes the yearly scientific production of publications in the field of HR and I4.0 according to the most important information gathered from the Scopus database.

Developments and Trends in I4.0 and HR Research
The analysis from the Bibliometrix package for R-Studio shows that the study of I4.0 and HR has 217 different bibliography sources and 354 different documents written by 1158 authors. In addition, the average of co-authors per document is 3.5. Regarding the annual scientific production between 2014 and 2023 (Table 5 and Figure 1), it is notable that, in 2015, only two articles were published, which indicates the starting point of academic publications (journals) concerning I4.0. It also becomes evident that, after a slight growth, there is an increase from 25 publications in 2021 to 66 articles published in 2020. Subsequently, the values rise to 75 in 2021 and 106 in 2022. Consequently, the year 2022 presents the highest number of publications within the investigated period. As of August 2023, the year has recorded half (53) of the publications made in 2022. This indicates a trend of stagnation in publications.  Figure 2 depicts the annual scientific output of researchers on the investigated theme. Table 5 illustrates the yearly count of articles published on the subject of Industry 4.0 and Human Resources. The present investigation examines the global and local citation of publications concerning the significance of articles in the field of I4.0. Global citation measures the number of times a work has been cited across the entire database (Scopus database), while local citation indicates the number of citations for the articles included in the analyzed dataset [20,21]. starting point of academic publications (journals) concerning I4.0. It also becomes e that, after a slight growth, there is an increase from 25 publications in 2021 to 66 a published in 2020. Subsequently, the values rise to 75 in 2021 and 106 in 2022. C quently, the year 2022 presents the highest number of publications within the invest period. As of August 2023, the year has recorded half (53) of the publications made i This indicates a trend of stagnation in publications. Figure 2 depicts the annual scientific output of researchers on the investigated  Table 5 illustrates the yearly count of articles published on the subject of Industry 4.0 and Human Resources.   The present investigation examines the global and local citation of publications concerning the significance of articles in the field of I4.0. Global citation measures the number of times a work has been cited across the entire database (Scopus database), while local citation indicates the number of citations for the articles included in the analyzed dataset [20,21]. The most globally cited article in the Scopus database ( Figure 4) is Benešová and Tupa [22], with 313 citations. Figure 5 displays the 20 most cited articles on Industry 4.0 and human resources. It is worth noting that most studies (Table 6) received more global than local citations. This might indicate low cases of self-citations. I4.0 and HR has a total of 354 documents based on the dataset, of which 36 journals have 20 or more citations (Figure 3). The list of the most locally cited sources is Procedia Cirp, with 215 citations, followed by Sustainability with 193 citations.
The most globally cited article in the Scopus database ( Figure 4) is Benešová and Tupa [22], with 313 citations.   It is worth noting that most studies (Table 6) received more global than local citations. This might indicate low cases of self-citations.

Scientific Publication by Region/Countries, Prolific Scholars, Affiliations, and Social Networks
This study also presents the number of publications by countries of the main author. Table 7 and Figure 6 show the top 20 most referenced countries' research work in the fields of I4.0 and HR.  In Figure 6, the stronger the shade of blue, the higher the scientific output of the country regarding Industry 4.0 and human resources. Italy is the country with the highest number of publications cited, followed by the Czech Republic, India, the United Kingdom, and Brazil (Table 7). In addition, the papers published in Indian, Italian, and Brazilian academic journals have a significant impact on the I4.0 field.
The results also present the top 20 researchers with the highest number of publications and citations in the field of I4.0 and HR from 2014 to 2023 based on the dataset (Figure 7 and Table 8). In Figure 6, the stronger the shade of blue, the higher the scientific output of the country regarding Industry 4.0 and human resources. Italy is the country with the highest number of publications cited, followed by the Czech Republic, India, the United Kingdom, and Brazil (Table 7). In addition, the papers published in Indian, Italian, and Brazilian academic journals have a significant impact on the I4.0 field.
The results also present the top 20 researchers with the highest number of publications and citations in the field of I4.0 and HR from 2014 to 2023 based on the dataset (Figure 7 and Table 8). In Figure 6, the stronger the shade of blue, the higher the scientific output of the country regarding Industry 4.0 and human resources. Italy is the country with the highest number of publications cited, followed by the Czech Republic, India, the United Kingdom, and Brazil (Table 7). In addition, the papers published in Indian, Italian, and Brazilian academic journals have a significant impact on the I4.0 field.
The results also present the top 20 researchers with the highest number of publications and citations in the field of I4.0 and HR from 2014 to 2023 based on the dataset (Figure 7 and Table 8).   In Figure 7, (i) the lines represent time, (ii) the size of the bubble represents the number of articles published by an author in a given year, (iii) the intensity of the color of the bubble represents the total number of citations in each year, (iv) the first bubble on the line represents the year in which the author started publishing in the area, (v) larger bubbles represent a higher number of articles published in that year, and (vi) bubbles with a more intense color represent a higher citation coefficient [20].
Regarding the category of publishing institutions and collaboration networks, the top 20 institutions and authors' affiliations contributing to I4.0 and HR can be seen in Figure 8. The University of Johannesburg in South Africa and the University of Zagreb in Croatia occupy the top position with 16 papers in total, followed by Cebu Technological University in the Philippines with 12 papers. Table 8 displays the researchers with the highest number of publications and citations in the field of Industry 4.0 and human resources.

Thematic Focus of the Fields of I4.0 and HR
This section analyzes the topics that have dominated studies in the fields of I4.0 and HR that researchers have focused on over the years. This part begins with an examination of keywords and their frequency of occurrences, followed by an examination of trending subjects and thematic sections of the field.
The keyword analysis aids in determining the topic and focus of the article. Figure 9 exhibits word clouds of commonly used terms in the Scopus fields: titles, keywords, and abstracts. The University of Johannesburg in South Africa and the University of Zagreb in Croatia occupy the top position with 16 papers in total, followed by Cebu Technological University in the Philippines with 12 papers. Table 8 displays the researchers with the highest number of publications and citations in the field of Industry 4.0 and human resources.

Thematic Focus of the Fields of I4.0 and HR
This section analyzes the topics that have dominated studies in the fields of I4.0 and HR that researchers have focused on over the years. This part begins with an examination of keywords and their frequency of occurrences, followed by an examination of trending subjects and thematic sections of the field.
The keyword analysis aids in determining the topic and focus of the article. In addition, Figure 10 shows the exponential growth of keywords in the studies of I4.0 and human resources management in the time period from 2014 to 2023. Conversely, this particular subject has received less attention in the domains of industrial enterprise and education. Despite being in the spotlight since 2015, the themes of human resources management and Industry 4.0 continued to rise exponentially after 2019, with 113 and 103 mentions, respectively. This suggests that human resources management and Industry 4.0 have become widely debated issues among academics. Figure 11 depicts a tree map based on a calculation of the percentage of how often each phrase was mentioned in the journals. In addition, Figure 10 shows the exponential growth of keywords in the studies of I4.0 and human resources management in the time period from 2014 to 2023. Conversely, this particular subject has received less attention in the domains of industrial enterprise and education. In addition, Figure 10 shows the exponential growth of keywords in the studies of I4.0 and human resources management in the time period from 2014 to 2023. Conversely, this particular subject has received less attention in the domains of industrial enterprise and education. Despite being in the spotlight since 2015, the themes of human resources management and Industry 4.0 continued to rise exponentially after 2019, with 113 and 103 mentions, respectively. This suggests that human resources management and Industry 4.0 have become widely debated issues among academics. Figure 11 depicts a tree map based on a calculation of the percentage of how often each phrase was mentioned in the journals. Despite being in the spotlight since 2015, the themes of human resources management and Industry 4.0 continued to rise exponentially after 2019, with 113 and 103 mentions, respectively. This suggests that human resources management and Industry 4.0 have become widely debated issues among academics. Figure 11 depicts a tree map based on a calculation of the percentage of how often each phrase was mentioned in the journals. The tree map shows (based on the title field of the search engine) that human resources management represents 14 percent of the investigations in the dataset, while Industry 4.0 accounts for 16 percent.
The authors' keywords from the Scopus database were also used in this study to carry out a trend analysis ( Figure 12). The following settings were specified: the time range was set to 2014-2023, the word minimum frequency was set to 5, the number of labels for each cluster was set to 3, and the label size was set to 0.3. Figure 12 shows a thematic map of the I4.0 and HR fields, which is divided into four quadrants (Q1 to Q4). Author Agbo [20] explains these quadrants as follows: the driving themes are represented by the upper right quadrant (Q1); the underlying themes are represented by the lower right quadrant (Q4); the specialized themes are represented by the upper left quadrant (Q2); and the emerging or disappearing themes are represented by the lower left quadrant (Q3). The tree map shows (based on the title field of the search engine) that human resources management represents 14 percent of the investigations in the dataset, while Industry 4.0 accounts for 16 percent.
The authors' keywords from the Scopus database were also used in this study to carry out a trend analysis ( Figure 12). The following settings were specified: the time range was set to 2014-2023, the word minimum frequency was set to 5, the number of labels for each cluster was set to 3, and the label size was set to 0.3. Figure 12 shows a thematic map of the I4.0 and HR fields, which is divided into four quadrants (Q1 to Q4). Author Agbo [20] explains these quadrants as follows: the driving themes are represented by the upper right quadrant (Q1); the underlying themes are represented by the lower right quadrant (Q4); the specialized themes are represented by the upper left quadrant (Q2); and the emerging or disappearing themes are represented by the lower left quadrant (Q3).
Notably, "employment human resource" is situated between Q21 and Q23, while "information management industry and human resource management" is placed between Q3 and Q4. In our case, the motor theme is represented by "employment".
The key subjects of Q1 are "decision-making" and "embedded systems", while Q2 has highly developed and specialized topics that connect to the leading theme. In our case, no topics could be identified for this part of the diagram, just a trend toward specialization of the "human resources" theme. Q3 has topics that are vanishing or emerging, such as "human resources productivity", while Q4 contains foundational and transversal themes, such as a trend of "sustainable development industry" and "human resource management".
The most related themes in the articles are observed in Figure 13. The graph was generated by factorial analysis. In the field item, the term "keywords Plus" was selected. The number of clusters was established automatically, and 20 terms were used. Notably, "employment human resource" is situated between Q21 and Q23, while "information management industry and human resource management" is placed between Q3 and Q4. In our case, the motor theme is represented by "employment".
The key subjects of Q1 are "decision-making" and "embedded systems", while Q2 has highly developed and specialized topics that connect to the leading theme. In our case, no topics could be identified for this part of the diagram, just a trend toward specialization of the "human resources" theme. Q3 has topics that are vanishing or emerging, such as "human resources productivity", while Q4 contains foundational and transversal themes, such as a trend of "sustainable development industry" and "human resource management".
The most related themes in the articles are observed in Figure 13. The graph was generated by factorial analysis. In the field item, the term "keywords Plus" was selected. The number of clusters was established automatically, and 20 terms were used. The red dot represents Cluster 1, encompassing a larger number of elements engaged in research within the I4.0 and HR theme. The red cluster indicates the relationship of Industry 4.0 with various themes, such as knowledge management, employment, sustainable development, human resources, sustainability, manufacturing, ergonomics, information management, decision making, manufacturing industries, industrial revolutions, supply chains, human resources management, industrial research, The red dot represents Cluster 1, encompassing a larger number of elements engaged in research within the I4.0 and HR theme. The red cluster indicates the relationship of In-dustry 4.0 with various themes, such as knowledge management, employment, sustainable development, human resources, sustainability, manufacturing, ergonomics, information management, decision making, manufacturing industries, industrial revolutions, supply chains, human resources management, industrial research, design/methodology/approach, personal training, and managers.
The blue triangle, on the other hand, signifies Cluster 2, characterized by a smaller set of analytical elements. The blue cluster focuses on systems/tools.
The thematic evolution of the articles can be observed in Figure 14. The graph was generated by factorial analysis considering "keywords Plus", 250 words, and 5 clusters frequency. Themes related to employees and human resources management have been in grated into Industry 4.0 research throughout the period from 2014 to 2023.

Discussion
The production of scientific papers on Industry 4.0 and human resources has show a strong increase since the year 2020 (66 articles). Silva et al. [40] consider this to be emerging field that needs to be comprehended to drive digital transformation. The fin ings of the present study support this perspective, given the high number of publicatio in 2020, 2021, and 2022, as well as the number of publications in 2023 (53 up to Augu surpassing that of 2019. It can be affirmed that the pursuit of understanding this field h been constant. Publications on Industry 4.0 and human resources have been prominently featur in management/business, applied sciences, and engineering journals. Noteworthy sour include Sustainability (26 articles), the Computers and Industrial Engineering journal (8 a cles), International Journal of Manpower (8 articles), and TQM Journal (8 articles). In terms citations, Procedia Cirp and Sustainability stand out (Figures 3 and 4). These mention journals exhibit a strong association with this field of study, as they receive contributio from diverse authors representing various academic disciplines.
The article by Benešová and Tupa [22] has received the highest number of citatio (313). The authors aimed to identify the existing roles in Industry 4.0 and present tren for the productive environment. Table 6 of the present study demonstrates that resear on the challenges of Industry 4.0 and requirements for worker qualification, as inve gated by Benešová and Tupa [22], constitute a significant trend in the field of Industry research, making their article a valuable reference for other works in this area.
Teplitskiy et al. [41] assert that highly cited articles have greater reader engageme influencing the research frontier. In this regard, the list of the most influential research in the field considers the average number of citations per publication for each research

Discussion
The production of scientific papers on Industry 4.0 and human resources has shown a strong increase since the year 2020 (66 articles). Silva et al. [40] consider this to be an emerging field that needs to be comprehended to drive digital transformation. The findings of the present study support this perspective, given the high number of publications in 2020, 2021, and 2022, as well as the number of publications in 2023 (53 up to August) surpassing that of 2019. It can be affirmed that the pursuit of understanding this field has been constant.
Publications on Industry 4.0 and human resources have been prominently featured in management/business, applied sciences, and engineering journals. Noteworthy sources include Sustainability (26 articles), the Computers and Industrial Engineering journal (8 articles), International Journal of Manpower (8 articles), and TQM Journal (8 articles). In terms of citations, Procedia Cirp and Sustainability stand out (Figures 3 and 4). These mentioned journals exhibit a strong association with this field of study, as they receive contributions from diverse authors representing various academic disciplines.
The article by Benešová and Tupa [22] has received the highest number of citations (313). The authors aimed to identify the existing roles in Industry 4.0 and present trends for the productive environment. Table 6 of the present study demonstrates that research on the challenges of Industry 4.0 and requirements for worker qualification, as investigated by Benešová and Tupa [22], constitute a significant trend in the field of Industry 4.0 research, making their article a valuable reference for other works in this area.
Teplitskiy et al. [41] assert that highly cited articles have greater reader engagement, influencing the research frontier. In this regard, the list of the most influential researchers in the field considers the average number of citations per publication for each researcher. The top 10 researchers with the highest average citation per publication are Battini, Bag, Vrchota, Stacho, Stachová, Jerman, Rehoř, Upadhyay, Germani, and Grenčíková.
Among the top five ranked researchers, Daria Battini from the Department of Management and Engineering at the University of Padua in Italy is the most influential scholar. Surajit Bag, the researcher with the second-highest coefficient, is affiliated with the Department of Transport and Supply Chain Management, University of Johannesburg (South Africa). Vrchota, the third-most influential researcher, is affiliated with South Bohemia University, where he serves as the deputy chairman of the Department of Management and is a member of the Academic Senate. The universities that excelled in knowledge production on Industry 4.0 and human resources are not located in the countries with the highest number of cited publications. The countries with the highest citation counts were Italy, the Czech Republic, India, the United Kingdom, and Brazil ( Figure 6, Table 7). Conversely, the universities with the highest number of articles are located in South Africa, Croatia, and the Philippines (Figure 8). This suggests that the countries with the most cited publications were not driven by specific universities.
As shown in the thematic analysis of previously published work related to the field of Industry 4.0 and human resources management, it was possible to identify different information to help describe past developments and future trends in this field. According to the top 10 most-cited references based on the number of global citations (Table 6), the following topics became apparent: requirements in education to qualify prospective professionals and industry workers; main challenges and drivers; war of talents; operation management is at the heart of the development; smart HRM concepts and approaches; and interest of specific service industries such as the hospitality sector. Regarding the degree of development and relevance, the analysis pointed to main themes that are highly relevant and growing, such as the following: a discussion about decision-making processes, embedded systems, and automation; emerging themes that are developing slowly and are somehow relevant, such as human resources management, sustainability, and manufacturing; basic themes that are highly relevant but slow in growth, such as sustainable development, human resources management, and engineering education; and central to the field's relevance and development are topics such as the service industry and employment. To summarize, the results highlight that, especially in the field of education, sustainability and new concepts of HRM are at the forefront of the field.
These findings imply that the concept of I4.0 is a cross-cutting theme that, amongst others, has received attention in not only the robotics, manufacturing, and automation industries (e.g., cyber-physical systems, embedded systems, Internet of Things, industrial research, artificial intelligence (AI), and smart manufacturing; see, for example, Ivanov et al. [42]) but also in the field of human resources management. It supports the assumption made in the holistic model by Dhanpat et al. [1] that Industry 4.0 has an impact on the organization and HR strategy and addresses the challenges and opportunities that Industry 4.0 creates in the so-called fourth industrial revolution. However, many studies point to the need to respect the current changes in the nature of the corporate environment that calls for a varying set of management abilities, such as strategic HRM, effective information sharing, and/or the development of an innovative organizational culture that has a great influence on job performance [43]. The results in this systematic literature review show that further development and exploration are needed to identify the specific skills and competencies required for the I4.0 transformation, such as technical, methodological, social, and personal skills. In their bibliographic research, Hecklau et al. [44] identified personal skills in addition to mainly technical skills, such as compliance, flexibility, sustainable mindset, and ability to work under pressure, as the main drivers for the adoption of I4.0 concepts. Also, Jerman et al. [12] found in their bibliometric and topic analysis on future competencies at smart factories that HR strategies should focus on at least the following four aspects: (1) the possibility of developing workers in learning organizations, (2) technical training development for workers, (3) future engineering profiles and engineering education, and (4) the development of interpersonal relationship skills.
Research on Industry 4.0 has started to integrate themes related to human resources. Milichovský and Kuba [45] state that Industry 4.0 involves elements such as digitization and robotics, which have an impact on human resources management. In this sense, there is a demand for workers with sufficient qualifications. This seems to drive the relationship between these topics, particularly concerning education and training. The success of implementing Industry 4.0 relies on elements related to human resources, such as top management leadership, the formation of cross-functional teams, the provision of preparatory activities, and the execution of training initiatives [46].
The challenge in human resources management in Industry 4.0 is to place the human factor at the core of technological innovation. Advancing in worker engagement and empowerment enables companies to achieve productivity, innovation, and retention of human capital. Furthermore, research in this field can progress with the development of a framework directed toward sustainable human resources management [47].
Research on Industry 4.0 and human resources management also investigates the effects of artificial intelligence. Malik et al. [48] indicate that negative factors include job insecurity, drastic organizational changes, and data security breaches. On the other hand, flexibility, autonomy, innovation potential, and overall performance improvement are considered positive factors. In this context, the development of interpersonal skills becomes necessary to support technostress.
The themes related to mental disorders in Industry 4.0 remain underexplored ( Figure 13). This scenario is in line with Waldmann et al.'s [49] findings. The authors highlight a limited number of studies addressing quality of life, anxiety, and depression in the context of Industry 4.0. Such research is significant within a competitive work environment and amidst unemployment [50].
Regarding the practical implications of this study, the findings in this study may be used by policymakers in the vocational and higher education sectors, as well as human resource specialists and strategic management experts in organizations of all branches.

Conclusions
This paper aimed to investigate academic trends relating to the themes of Industry 4.0 and human resources.
Technology is the focus of Industry 4.0. A lot of the technology needed is already in place to replace much of the current HR-related activities. As a result, HR 4.0 is a revolution that must be studied in the field of human resources.
The increased demand for human resources skills is an important practical implication of Industry 4.0.
The papers about the theme essentially began to be published from 2020 onward. Sustainability is the most relevant source/journal, with 26 publications out of 354 articles published.
Italy is the country with the highest number of publications cited in the subject area, followed by the Czech Republic, India, the United Kingdom, and Brazil. The academic works that have been published in German and Italian publications have also had a considerable influence on the field of I4.0.