First Author:   Refk Selmi Business School of Tunis s.refk@yahoo.fr   , Campus Universitaire de la Manouba , 2100, Tunisie   21697675635(Phone) 21697675635(Fax) Second Author: Jamal Bouoiyour University of Pau jamal.bouoiyour@univ-pau.fr   , 64000, France