1. Department of Basic Science, Faculty of Mines and Petroleum Industries, University of Maroua, P.O. Box 08, , Cameroon
2. Department of Physics, Faculty of Science, The University of Maroua, P.O. Box 814, Maroua, Cameroon
3. Department of Mathematics, Huzhou University, Huzhou 313000, China
4. Hunan Provincial Key Laboratory of Mathematical Modeling and Analysis in Engineering, Changsha University of Science and Technology, Changsha 410114, China
5. Department of Mathematics, Science Faculty, Firat University, 23119 Elazig, Turkey
6. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan
7. Faculty of Engineering Technology, Amol University of Special Modern Technologies, Amol, Iran
8. Department of Physics, Faculty of Science, The University of Ngaoundere, P.O. Box 454, Ngaoundere, Cameroon