1. Department of Mathematics, Shanghai University, Shanghai 200444, China
2. Department of Mathematics, Zhejiang Normal University, Jinhua 321004, Zhejiang, China
3. Department of Mathematics, King Abdulaziz University, Jeddah, Saudi Arabia
4. International Institute for Symmetry Analysis and Mathematical Modelling, Department of Mathematical Sciences, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2735, South Africa