1. Department of Mathematics, Faculty of Science, Jiangsu University, Zhenjiang 212013 Jiangsu, P. R. China
2. Department of Mathematics, COMSATS University Islamabad, Islamabad Campus, Chak Shehzad, Islamabad, Pakistan
3. Department of Mathematics and Statistics, Riphah International University I-14, Islamabad 44000, Pakistan
4. Department of Mathematics, Huzhou University, Huzhou 313000, P. R. China
5. Hunan Provincial Key Laboratory of Mathematical Modeling and Analysis in Engineering, Changsha University of Science & Technology, Changsha 410114, P. R. China