First Author:   Obin Angbo University of Angers serge.angbo@yahoo.fr   177 Rue René Baulant Dammarie-les-Lys, 77190, France   0652915127(Phone) 0652915127(Fax) Second Author: François Gardes Paris 1 Pantheon-Sorbonne University francois.gardes@univ-paris1.fr   , France