Full paper in PDF:
$%A. Ouazzani, Algèbres de Lie associées a un système de Pfaff, Rev. Mat. Complut. 13 (2000),
no. 1, 183–192.%$
ABSTRACT
By using an invariant related to free Lie algebras, we give a criterion of non existence of isomorphism for the Pfaffian systems.
1991 Mathematics Subject Classification: 53C12, 17BXX, 58A17.