1. Ho Chi Minh City University of Industry and Trade , Ho Chi Minh City , Vietnam
2. Department of Mathematical Economics, Banking University of Ho Chi Minh City , Ho Chi Minh City , Vietnam
3. Faculty of Basic Science, Posts and Telecommunications Institute of Technology , Ho Chi Minh City , Vietnam
4. Falculty of Maths, FPT University HCM, Saigon Hi-tech Park , Ho Chi Minh City , Vietnam