1. Laboratory of Electronics and Signal Processing, Department of Physics, Faculty of Science, University of Dschang, P. O. Box 67 Dschang, Cameroon
2. Laboratory of Applied Mathematics, Department of Mathematics and Computer Science, Faculty of Science, University of Douala, P. O. Box 24157 Douala, Cameroon
3. Potsdam Institute for Climate Impact Research (PIK), Telegraphenberg A 31, 14412 Potsdam, Germany