Lian-Li Feng1, Shou-Fu Tian1,2, Xiu-Bin Wang1, Tian-Tian Zhang1
1Department of Mathematics and Center of Nonlinear Equations, China University of Mining and Technology, Xuzhou 221116, People’s Republic of China
2Department of Applied Mathematics and Theoretical Physics, University of Cambridge, CambridgeCB3 0WA, United Kingdom