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. 2021 Dec 17;48(6):705–720. doi: 10.1134/S1062359021060108

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© Pleiades Publishing, Inc. 2021, ISSN 1062-3590, Biology Bulletin, 2021, Vol. 48, No. 6, pp. 705–720. © Pleiades Publishing, Inc., 2021.

This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

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Fig. 8. — Keywords time zone diagram (timeline view): The heavier color is displayed, and closer the time is. The lines can also be seen that there is a clear relationship between the studies of different stages, indicating research is progressive.