1. Faculty of Basic Sciences, Vinh Long University of Technology Education, Vinh Long, Vietnam
2. Department of Mathematics, Teacher College, Can Tho University, Can Tho, Vietnam
3. Faculty of Mathematics and Computer Science, University of Science, Ho Chi Minh City, Vietnam + National University, Ho Chi Minh City, Vietnam + Faculty of Basic Sciences, Vinh Long University of Technology Education, Vinh Long, Vietnam