[1] Moscow MV Lomonosov State Univ, Fac Mech & Math, Kazakhstan Branch, Astana 010010, Kazakhstan
[2] Inst Math & Math Modeling, Alma Ata 050010, Kazakhstan
[3] Moscow MV Lomonosov State Univ, Fac Mech & Math, Dept Differential Equat, Moscow 119991, Russia
[4] Russian Acad Sci, Inst Math Comp Ctr, Subdiv Ufa Fed Res Ctr, Ufa 450008, Russia
[5] Russian Acad Sci, Inst Informat Transmiss Problems, Moscow 127051, Russia