V.S. Chesakov – Undergraduate, Saratov State University named after N.G. Chernyshevsky

E-mail: seva.chesakov@mail.ru, kof@info.sgu.ru

L.S. Sotov – Dr. Sc. (Eng.), Saratov State University named after N.G. Chernyshevsky E-mail: slskit@mail.ru, kof@info.sgu.ru