1. Department of Renewable Energies, National Higher PolytechnicSchool of Maroua, University of Maroua, P. O. Box 46, Maroua, Cameroon
2. Department of Fundamental Sciences, National Advanced School of Mines and Petroleum Industries, University of Maroua, P. O. Box 46, Maroua, Cameroon
3. School of Geology and Mining, University of Ngaoundere, Cameroon