1. Department of Differential Equations, Institute of Mathematics and Mathematical Modeling, 125, Pushkin Str.; and Laboratory of Mathematical Cybernetics and Computational Technologies, Institute of Information and Computational Technologies, 125, Pushkin Str., 050010, Almaty, Kazakhstan
2. Department of Differential Equations, Institute of Mathematics and Mathematical Modeling, 125, Pushkin Str., 050010, Almaty, Kazakhstan