https://hal.archives-ouvertes.fr/hal-00004738 Contributor : Olivier FruchartConnect in order to contact the contributor Submitted on : Sunday, April 17, 2005 - 9:03:02 PM Last modification on : Friday, June 10, 2022 - 9:16:03 AM Long-term archiving on: : Thursday, April 1, 2010 - 9:20:07 PM