First Author:   Jacques Simon Song University of Dschang, Cameroon sonjacques@yahoo.fr   Independence square Dschang, 110, Dschang (Cameroon), Cameroun   676249644(Phone) 676249644(Fax) Second Author: Hervé William Mougnol A Ekoula University of Yaoundé II, Soa, Cameroon wmougnol@yahoo.com   Yaoundé, 1365, Yaoundé (Cameroon), Cameroun       Third Author: Adalbert Abraham Ghislain Melingui Bate University of Dschang, Cameroon melibate@yahoo.fr   Independence square Dschang, 110, Dschang (Cameroon), Cameroun   676249644(Phone)