First Author:   François Pannequin Ecole Normale Supérieure de Cachan and CES francois.pannequin@ens-cachan.fr   CACHAN, 94235, FRANCE       Second Author: Anne Corcos LEM - University Paris 2 anne.corcos@u-picardie.fr   5/7 avenue Vavin, 5/7 avenue Vavin Paris, 75006, France       Third Author: Sacha Bourgeois-gironde University of Provence sbgironde@gmail.com   Institut Jean-Nicod, Ecole Normale Supérieure Paris, 75013, France   33 1 44322669(Phone)