1. Department of Mathematics, Art and Science Faculty, Siirt University, 56100 Siirt, Turkey
2. Department of Computer Science and Mathematics, Lebanese American University, Beirut P.O. Box 13-5053, Lebanon
3. Department of Mathematics, Mathematics Research Center, Near East University, Near East Boulevard, 99138 Mersin, Turkey
4. Instituto Universitario de Matemática Pura y Aplicada, Universitat Politècnica de València, 46022 València, Spain