1. Department of Mathematics, International University Vietnam National University-Ho Chi Minh City, Ho Chi Minh City, Vietnam
2. Department of Mathematics, Vietnam National University - Ho Chi Minh City (VNU-HCM), Ho Chi Minh City, Vietnam
3. Department of Optimization and System Theory, VNUHCM – University of Science, Ho Chi Minh city, Vietnam
4. Department of Natural Science, Tien Giang University, Tien Giang town, Vietnam