1. School of Mathematics and Statistics, Shandong University of Technology, Zibo, Shandong 255091, P. R. China
2. School of Mathematics and Statistics, Changsha University of Science and Technology, Changsha, Hunan 410114, P. R. China
3. Division of Computational Mathematics and Engineering, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam
4. Faculty of Mathematics and Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam
5. Chern Institute of Mathematics and LPMC, Nankai University, Tianjin 300071, P. R. China
6. Faculty of Economics, Chiang Mai University, Chiang Mai 52000, Thailand