1. Department of Mathematics, Teacher College, Cantho University, Cantho, Vietnam;
2. Division of Computational Mathematics and Engineering, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam;
3. Faculty of Mathematics and Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam;
4. Faculty of Mathematics and Computer Science, University of Science, Vietnam National University, Ho Chi Minh City, Vietnam;
5. Department of Mathematics, Ho Chi Minh City University of Food Industry, Ho Chi Minh City, Vietnam