a Institute of Mathematics and Mechanics, National Academy of Sciences of Azerbaijan, Baku, AZ1141 Azerbaijan
b Baku State University, Baku, AZ1148 Azerbaijan
c Institute of Control Systems, National Academy of Sciences of Azerbaijan, Baku, AZ1141 Azerbaijan
Correspondence to: *e-mail: misir.mardanov@imm.az
Correspondence to: **e-mail: misirmardanov@yahoo.com
Correspondence to: ***e-mail: t.melik@rambler.ru
Received 26 June, 2018
DOI: 10.1134/S1064562418070049