https://cel.archives-ouvertes.fr/cel-00688936 Contributor : Badr BenmammarConnect in order to contact the contributor Submitted on : Wednesday, April 18, 2012 - 11:39:25 PM Last modification on : Thursday, April 19, 2012 - 8:36:26 AM Long-term archiving on: : Thursday, July 19, 2012 - 2:32:38 AM