1. Department of Basic Teaching, Anhui Sanlian University, Hefei 230601, P. R. China
2. Department of Mathematics, Faculty of Basic Sciences, Bozorgmehr University of Qaenat, Qaen, Iran
3. Department of Mathematics, Quchan University of Technology, Quchan, Iran
4. Department of Mathematical Sciences, University of South Africa, UNISA0003, South Africa
5. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 110122, Taiwan