https://cel.archives-ouvertes.fr/cel-00391947 Contributor : Cimpa CimpaConnect in order to contact the contributor Submitted on : Friday, June 5, 2009 - 11:09:45 AM Last modification on : Friday, June 5, 2009 - 10:53:55 PM Long-term archiving on: : Thursday, June 10, 2010 - 8:42:49 PM