https://cel.archives-ouvertes.fr/cel-00392131 Contributor : Cimpa CimpaConnect in order to contact the contributor Submitted on : Friday, June 5, 2009 - 3:34:39 PM Last modification on : Friday, June 5, 2009 - 10:58:07 PM Long-term archiving on: : Friday, June 11, 2010 - 12:23:06 AM