1. Department of Mathematics-Informatics, Ho Chi Minh University of Pedagogy, Ho Chi Minh city, Vietnam
2. Faculty of Mathematics and Computer Science, University of Science, Vietnam National University, Ho Chi Minh City, Vietnam
3. Basic Scientific Faculty, Foreign Trade University, Hochiminh City Campus, 15 D5 Street, Ward 25, Binh Thanh District, Hochiminh, Vietnam
4. Department of Natural Science Education, Dong Nai University, Dong Nai, Vietnam