1. Department of Mathematics, Ahi Evran University, Kirsehir, Turkey
2. Institute of Applied Mathematics, Baku State University, Baku, AZ 1148, Azerbaijan
3. RUDN University, Moscow, 117198, Russian Federation
4. Institute of Mathematics and Mechanics of NAS of Azerbaijan, Baku, Azerbaijan
5. Baku State University, Baku, Azerbaijan
6. Dipartimento di Matematica e Informatica, Universitá di Catania, Catania, Italy