1. Xing Zhi College of Xi’an University of Finance and Economics, Xi’an City, Shaanxi Province, P. R. China
2. Department of Applied Mathematics, Faculty of Mathematical Sciences, University of Tabriz, Tabriz, Iran
3. Natural Sciences Faculty, Lankaran State University, 50, H. Aslanov Street, Lankaran, Azerbaijan
4. Department of Mathematics, Faculty of Science, Al-Azhar University, Nasr City, P. N. Box: 11884 Cairo, Egypt
5. Department of Mathematics, Faculty of Science and Art, Nevsehir Haci Bektas Veli University, Nevsehir 50300, Turkey
6. Mathematics Department, College of Science, University of Kirkuk, Kirkuk, Iraq