Saransk SayapinaNatalyaNikolaevna Saratov State University , 83, Astrakhanskaya str., Saratov, 410002, Russia sayapinanat@mail.ru Read more about Sayapina Natalya Nikolaevna NikishovaNatalyaV. Saransk Cooperative Institute (Branch) of the Russian University of Cooperation, 17, Transportnaya St., Saransk, 430027, Republic of Mordovia, Russia nikishova.2011@mail.ru Read more about Nikishova Natalya V. KevbrinBorisFedorovich Saransk Cooperative Institute (Branch) of the Russian University of Cooperation, 17, Transportnaya St., Saransk, 430027, Republic of Mordovia, Russia bkevbrin@rucoop.ru Read more about Kevbrin Boris Fedorovich
