References
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1. J. EL GHARIB and C. CHAVANT, "Calibration on triaxial tests of a viscoplastic behavior law for argillite based on the Drucker_Prager model", H-T64-2008-04194-FR,


2. J. EL GHARIB and C. CHAVANT, "Implementation of a simplified viscoplastic model in Code_Aster", H-T64-2007-01800-FR,