First Author:   Ben Mbarek Hassene ESSEC business school Tunisia, University of Tunis hassene_mbarek@yahoo.fr   22 rue ammar haji menzah 9 B Tunis, 1013, Tunisie   53948946(Phone) 53948946(Fax) Second Author: Jday Dorsaf ESSEC BUSINSS SCHOOL tunisia, University of Tunis dorsafjday20@gmail.com