https://hal-paris1.archives-ouvertes.fr/hal-02404160 Contributor : Alain DuplouyConnect in order to contact the contributor Submitted on : Wednesday, December 18, 2019 - 10:29:20 AM Last modification on : Friday, April 29, 2022 - 10:12:38 AM Long-term archiving on: : Thursday, March 19, 2020 - 12:47:31 PM