1. Faculty of Mathematical Economics Banking University of Ho Chi Minh City Ho Chi Minh City Vietnam
2. Pedagogical Department E. E., Section of Mathematics and Informatics National and Capodistrian University of Athens Athens Greece
3. Division of Computational Mathematics and Engineering Institute for Computational Science, Ton Duc Thang University Ho Chi Minh City Vietnam
4. Faculty of Mathematics and Statistics Ton Duc Thang University Ho Chi Minh City Vietnam