1. Department of Physics, Faculty of Science, The University of Maroua, P.O. Box 814, Maroua, Cameroon
2. Firat University, Science Faculty, Department of Mathematics, 23119 Elazig, Turkey
3. Department of Physics, Faculty of Science, The University of Ngaoundere, P.O. Box 454, Cameroon
4. Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
5. Faculty of Natural Sciences, Duy Tan University, Da Nang 550000, Vietnam