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Sustainability
Volume 18
Issue 10
10.3390/su18105184
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Retraction of Sustainability 2021, 13(24), 14024.
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Retraction

RETRACTED: Stoyanova et al. System-Cluster Technology of e-Learning Improvement Under the Conditions of COVID-19. Sustainability 2021, 13, 14024

by
Tsvetana Stoyanova
1,
Philip Stoyanov
1,
Anzhelika Remnova
2,
Svitlana Kushniruk
2,
Lyudmyla Rakityanska
3 and
Svetlana Drobyazko
4,*
1
Department of Management, University of National and World Economy, 1700 Sofia, Bulgaria
2
Department of Pedagogy, Dragomanov National Pedagogical University, 01601 Kyiv, Ukraine
3
Department of Pedagogy, Kryvyi Rih State Pedagogical University, 50000 Kryvyi Rih, Ukraine
4
The European Academy of Sciences Ltd., London WC2H 9JQ, UK
*
Author to whom correspondence should be addressed.
Sustainability 2026, 18(10), 5184; https://doi.org/10.3390/su18105184
Submission received: 19 May 2026 / Accepted: 20 May 2026 / Published: 21 May 2026
Versions Notes
The journal retracts the article “System-Cluster Technology of e-Learning Improvement under the Conditions of COVID-19” [1] cited above.
Following publication, concerns were brought to the attention of the Editorial Office regarding the overlap between this publication [1] and an unpublished habilitation thesis in another language [2] produced by a different author.
Adhering to our complaint procedure, an investigation was conducted by the Editorial Office and Editorial Board; a significant overlap in the text and figures was confirmed. Given the extent of the overlap, the Editorial Board has decided to retract this publication [1], as per MDPI’s retraction policy (https://www.mdpi.com/ethics#_bookmark30, accessed on 19 May 2026).
This retraction was approved by the Editor-in-Chief of the journal Sustainability.
The authors did not agree to this retraction.

References

  1. Stoyanova, T.; Stoyanov, P.; Remnova, A.; Kushniruk, S.; Rakityanska, L.; Drobyazko, S. RETRACTED: System-Cluster Technology of e-Learning Improvement under the Conditions of COVID-19. Sustainability 2021, 13, 14024. [Google Scholar] [CrossRef]
  2. Volov, V.T. System-Cluster Theory and Technology for Improving the Quality of Distance Education in Higher Education. Ph.D. Thesis, Kazan Federal University, Kazan, Russia, 2000. [Google Scholar]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

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MDPI and ACS Style

Stoyanova, T.; Stoyanov, P.; Remnova, A.; Kushniruk, S.; Rakityanska, L.; Drobyazko, S. RETRACTED: Stoyanova et al. System-Cluster Technology of e-Learning Improvement Under the Conditions of COVID-19. Sustainability 2021, 13, 14024. Sustainability 2026, 18, 5184. https://doi.org/10.3390/su18105184

AMA Style

Stoyanova T, Stoyanov P, Remnova A, Kushniruk S, Rakityanska L, Drobyazko S. RETRACTED: Stoyanova et al. System-Cluster Technology of e-Learning Improvement Under the Conditions of COVID-19. Sustainability 2021, 13, 14024. Sustainability. 2026; 18(10):5184. https://doi.org/10.3390/su18105184

Chicago/Turabian Style

Stoyanova, Tsvetana, Philip Stoyanov, Anzhelika Remnova, Svitlana Kushniruk, Lyudmyla Rakityanska, and Svetlana Drobyazko. 2026. "RETRACTED: Stoyanova et al. System-Cluster Technology of e-Learning Improvement Under the Conditions of COVID-19. Sustainability 2021, 13, 14024" Sustainability 18, no. 10: 5184. https://doi.org/10.3390/su18105184

APA Style

Stoyanova, T., Stoyanov, P., Remnova, A., Kushniruk, S., Rakityanska, L., & Drobyazko, S. (2026). RETRACTED: Stoyanova et al. System-Cluster Technology of e-Learning Improvement Under the Conditions of COVID-19. Sustainability 2021, 13, 14024. Sustainability, 18(10), 5184. https://doi.org/10.3390/su18105184

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