Trace Elements Zinc and Selenium: Their Significance in the Conditions of the COVID-19 Pandemic von Gulich, M.P., Yemchenko, N.L., Kaplinenko, V.G., Kharchenko, O.O., Гуліч, М.П., Ємченко, Н.Л., Каплуненко, В.Г., Харченко, О.О.