1. L2MPS, Department of Physics Faculty of Science, University of Dschang Dschang Cameroon
2. LEMAP, Department of Physics Faculty of Science, University of Yaounde 1 Yaoundé Cameroon
3. Earth System Physics Section Abdus Salam ICTP Trieste Italy
4. School of Wood, Water and Natural Resources Faculty of Agronomy and Agricultural Sciences, University of Dschang Ebolowa Cameroon