Pertseva, T. O., et al. “PECULIARITIES OF LEVEL OF THE GASTROINTESTINAL TRACT IN CORONAVIRUS DISEASE (COVID-19) IN DIFFERENT WAVES OF THE PANDEMIC”. Achievements of Clinical and Experimental Medicine, no. 4, Mar. 2022, pp. 151-5, doi:10.11603/1811-2471.2021.v.i4.12514.