1. School of Mathematics and Computer Science, Yunnan Minzu University, Kunming 650500, China
2. College of Mathematics and Information Science, Shaanxi Normal University, Xi'an 710062, China
3. Three Gorges Mathematical Research Center, China Three Gorges University, Yichang 443002, China
4. Laboratory for Industrial and Applied Mathematics, York University, Toronto M3J 1P3, Canada
5. Department of Mathematics, Hubei Minzu University, Enshi 445000, China
6. Department of Applied Mathematics, University of Waterloo, Waterloo N2L 3G1, Canada