https://cel.archives-ouvertes.fr/cel-00391781 Contributor : Cimpa CimpaConnect in order to contact the contributor Submitted on : Thursday, June 4, 2009 - 4:45:44 PM Last modification on : Friday, June 5, 2009 - 11:15:27 PM Long-term archiving on: : Monday, October 15, 2012 - 11:46:29 AM