1. Department of Mathematics, Science Faculty, Firat University , Elazig , 23119 , Turkey
2. Department of Medical Research, China Medical University Hospital, China Medical University , Taichung , Taiwan
3. Faculty of Industrial Engineering of the University of Douala , Douala , Cameroon
4. Department of Physics, Faculty of Science, The University of Maroua , P.O. Box 814 , Maroua , Cameroon
5. Department of Mathematics, Huzhou University , Huzhou , 313000 , China
6. Hunan Provincial Key Laboratory of Mathematical Modeling and Analysis in Engineering, Changsha University of Science and Technology , Changsha , 410114 , China