First Author:   Issa Dianda Thomas Sankara University isdianda@yahoo.fr   Ouagadougou, Burkina Faso   +226 70 59 50 53(Phone) +226 70 59 50 53(Fax) Second Author: Idrissa Ouedraogo Panafrican University and the University of Yaoundé II pridrissoued87@yahoo.fr   Yaoundé, Cameroon       Third Author: Jean de dieu Goumbri Thomas Sankara University goumbrijeandedieu@yahoo.fr   Ouagadougou, Burkina Faso   +226 71 06 89 09(Phone)