1. Department of Physics, Faculty of Science, Pure Physics, Laboratory, Group of Nonlinear Physics and Complex Systems, University of Douala, P.O. Box 24157, Douala, Cameroon
2. Department of Base Scientific Education, Advanced Teacher’s Training College of the Technical Education, University of Douala, P.O. Box 8213, Douala, Cameroon
3. Department of Physics, School of Geology and Mining Engineering, University of Ngaoundéré, P.O. Box 115 Meiganga, Cameroon
4. Department of Civil Engineering, Advanced Teacher’s Training College of the Technical Education, University of Douala, P.O. Box 8213, Douala, Cameroon