1. Department of Mathematics, Hanshan Normal University, Chaozhou 515041, P. R. China
2. School of Mathematical Science, Shanghai Jiao Tong University, Shanghai, P. R. China
3. Department of Mathematics, University of Malakand, Chakdara Dir (Lower), Khyber Pakhtunkhwa, Pakistan
4. Department of Mathematics, King Saud University, P. O. Box 22452, Riyadh 11495, Saudi Arabia
5. Department of Mathematics, University of Malakand, Chakdara Dir (Lower), 18000 Khyber Pakhtunkhwa, Pakistan
6. Department of Computer Engineering, Biruni University, Istanbul, Turkey
7. Department of Mathematics, Faculty of Science, Firat University, 23119 Elaziğ, Turkey
8. Department of Medical Research, China Medical University, Taichung, Taiwan
9. Department of Mathematics, Lafayette College, Easton, PA, USA