1. 1Siirt University, Art and Science Faculty, Department of Mathematics, TR-56100 Siirt, Turkey
2. 2Çankaya University, Faculty of Arts and Sciences, Department of Mathematics and Computer Sciences, 06530 Ankara, Turkey; Institute of Space Sciences, Magurele, Bucharest, Romania
3. 3FIrat University, Science Faculty, Department of Mathematics, 23119 ElazIğ, Turkey
4. 4Mathematics Department, College of Science (Malaz), King Saud University, P.O. Box 22452 Riyadh, Kingdom of Saudi Arabia