Affiliation: | 1. Faculty of Mathematics and Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam;2. Faculty of Mathematics and Computer Science, University of Science, Vietnam National University Ho Chi Minh City, Ho Chi Minh City, Vietnamcaoxuanphuong@tdt.edu.vn;4. Faculty of Mathematics and Computer Science, University of Science, Vietnam National University Ho Chi Minh City, Ho Chi Minh City, Vietnam;5. Centre for Mathematical Science, University of Science, Vietnam National University Ho Chi Minh City, Ho Chi Minh City, Vietnam |