https://hal.archives-ouvertes.fr/hal-03200981 Contributor : Gérard POGORELConnect in order to contact the contributor Submitted on : Wednesday, April 21, 2021 - 12:08:46 PM Last modification on : Thursday, April 7, 2022 - 3:40:26 AM Long-term archiving on: : Thursday, July 22, 2021 - 6:07:04 PM