https://cel.archives-ouvertes.fr/cel-00637008 Contributor : Raphaele HerbinConnect in order to contact the contributor Submitted on : Friday, October 28, 2011 - 10:30:50 PM Last modification on : Thursday, October 28, 2021 - 3:25:28 AM Long-term archiving on: : Monday, January 30, 2012 - 11:18:47 AM