1. School of Science, Hunan City University, Yiyang 413000, P. R. China
2. Department of Mathematics, Riphah International University I-14, Islamabad, Pakistan
3. Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan
4. Department of Studies and Research in Mathematics, Davangere University, Davangere Karnataka, India
5. Department of Mathematics, COMSATS University Islamabad, Sahiwal 57000, Pakistan
6. Department of Mathematics, Huzhou University, Huzhou 313000, P. R. China
7. Hunan Provincial Key Laboratory of Mathematical Modeling and Analysis in Engineering Changsha University of Science and Technology, Changsha 410114, P. R. China