1. Department of Mathematics, Government College University, Faisalabad 38000, Pakistan
2. Department of Mathematics, Government College Women University, Faisalabad, Pakistan
3. University of Massachusetts Medical School, Worcester, MA 01655, USA
4. Department of Mathematics, Huzhou University, Huzhou 313000, P. R. China
5. Institute for Advanced Study Honoring Chen Jian Gong, Hangzhou Normal University, Hangzhou 311121, P. R. China