1. College of mathematics, Huaibei Normal University, 235000 Huaibei, P. R. China
2. Nanchang Institute of Technology, Nanchang 330044, P. R. China
3. Division of Biochemistry, Department of Pharmacology, College of Pharmacy, Taif University, P. O. Box 11099, Taif 21944, Saudi Arabia
4. Department of Mathematics, Faculty of Science, Jiangsu University, 212013 Zhenjiang, P. R. China
5. Department of Mathematics, Obour High Institute for Engineering and Technology, 11828 Cairo, Egypt