[1] Department of Fundamental and Applied Sciences, Mathematics and Computing Laboratory, Nangui Abrogoua University, Côte d'Ivoire, 02, Abidjan 02, Abidjan,BP 801, Ivory Coast
[2] Department of Mathematics and Industrial Engineering Polytechnique Montreal, P.O. Box 6079, Station Centre-ville, Montréal,QC,H3C 3A7, Canada