Kursk VostrikovPavelV.Kursk State University, 33 Radishcheva St., Kursk 305000, RussiaSortavala2015@inbox.ru Read more about Pavel V. Vostrikov MakarovaDarjaYurjevnaKursk State University, 33 Radishcheva St., Kursk 305000, Russiaveter-s-gor@yandex.ru Read more about Makarova Darja Yurjevna BelevtsevaSvetlanaN.Kursk State University, 33 Radishcheva St., Kursk 305000, RussiaSNBelevtseva@yandex.ru Read more about Svetlana N. Belevtseva