Minsk KorolekО.V.Belarusian State University, Prospect Nezavisimosti, 4, 220030, city Minskolga_zinchuk@tut.by Read more about Королик Ольга Васильевна DrozdovN.А.Belarusian State University, Prospect Nezavisimosti, 4, 220030, city Minskdrozdov@bsu.by Read more about Дроздов Николай Александрович