1. School of Science, Xi’an Shiyou University, Xi’an, Shaanxi, China
2. School of Mathematics, Northwest University, Xi’an, P.R. China
3. School of Mathematics and Information Science, Shaanxi Normal University, Xi’an, P.R. China
4. Mahani Mathematical research center, Shahid Bahonar University of Kerman, Kerman, Iran
5. Department of Pure Mathematics, Faculty of Mathematics and Computer, Shahid Bahonar University of Kerman, Kerman, Iran