TY JOUR TI COVID-19 Pandemic Course 2020–2022: Description by Methods of Mathematical Statistics and Discrete Mathematical Analysis KW COVID-19 KW DMA KW statistics KW data analysis JO Russian Journal of Earth Sciences AU Gvishiani, A.D. AU Odintsova, A.A. AU Rovenskaya, E.A. AU Boyarshinov, G.. AU Belov, I.O. AU Dobrovolsky, M.N. PY 2023 IS 23 PB Geophysical Center of the Russian Academy of Sciences