**Author details**

Lyudmila Alexeyeva<sup>1</sup> \* and Yergali Kurmanov1,2

1 Institute of Mathematics and Mathematical Modeling, Almaty, Kazakhstan

2 Al Farabi Kazakh National University, Almaty, Kazakhstan

\*Address all correspondence to: alexeeva@math.kz

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
