1. School of Mathematical Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, China
2. Institute of Chemical Engineering and Technology, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590, Pakistan
3. Department of Physics, Zhejiang Normal University, Jinhua 321004, P. R. China
4. Jiangsu Key Laboratory for NSLSCS, School of Mathematical Sciences, Nanjing Normal University, Nanjing 210023, P. R. China