I.V. Chepkasov - Ph.D. (Phys.-Math.), Khakas State University, Abakan. E-mail: ilya_chepkasov@mail.ru
Yu.Ya. Gafner - Dr.Sc. (Phys.-Math.), Professor, Head of Department, Katanov Khakass State University, Abakan. Е-mail: ygafner@khsu.ru

V.S. Baidyshev - Ph.D. (Phys.-Math.), Khakas State University, Abakan Yu.Ya. Gafner - Dr.Sc. (Phys.-Math.), Professor, Head of Department, Khakas State University, Abakan