Cheboksary GavrilovArtyomDmitrievich Chuvash State University, 428015, Russia, Chuvash Republic, Cheboksary, Moskovsky Avenue, 15 artmaster28@rambler.ru Read more about Gavrilov Artyom Dmitrievich VasilyevaLudmilaAlexandrovna Chuvash State University, 428015, Russia, Chuvash Republic, Cheboksary, Moskovsky Avenue, 15 milavas71@mail.ru Read more about Vasilyeva Ludmila Alexandrovna NikitinaAlyonaYuryevna Chuvash State University, 428015, Russia, Chuvash Republic, Cheboksary, Moskovsky Avenue, 15 alyona.nikitina@gmail.com Read more about Nikitina Alyona Yuryevna