1. Research Unit Condensed Matter, Electronics and Signal Processing, University of Dschang, P.O. Box 67, Dschang, Cameroon
2. Center for Interdisciplinary Research on Complex Systems, University of Sao Paulo, Av. Arlindo Bettio 1000, 03828-000 São Paulo, Brazil
3. Department of Physics-FFCLRP, University of São Paulo, Ribeirao Preto, SP 14040-901, Brazil
4. L2MSP, University of Dschang, P.O. Box 67, Dschang, Cameroon
5. São Paulo State University (UNESP), Instituto de Física Teórica, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra Funda, 01140-070 São Paulo, Brazil