1. Research Group on Experimental and Applied Physics for Sustainable Development, Faculty of Science, Department of Physics, University of Dschang, P. O. Box 412, Dschang, Cameroon
2. Laboratory of Condensed Matter, Electronics and Signal Processing, Department of Physics, University of Dschang, P. O. Box 067, Dschang, Cameroon
3. Department of Physics, Higher Teacher Training College, University of Bamenda, P. O. Box 39, Bamenda, Cameroon
4. Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, Ulm 89069, Germany
5. Instituto de Fisica Teorica – UNESP, Universidade Estadual Paulista, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra Funda, 01140-070 Sao Paulo, Brazil
6. Laboratoire de Mécanique et de Modélisation des Systèmes, L2MS, Department of Mathematics and Computer Science, Faculty of Science, University of Dschang, P. O. Box 67, Dschang, Cameroon