1. Division of Applied Mathematics, Thu Dau Mot University, Binh Duong Province, Vietnam
2. Department of Mathematics, Cankaya University, 06790 Etimesgut, Ankara, Turkey
3. Department of Medical Research, China Medical University Hospital, China Medical University, 40402 Taichung, Taiwan
4. Department of Mathematics and Computer Sciences, Transilvania University of Brasov, Brasov, Romania