Presymplectic lagrangian systems. I : the constraint algorithm and the equivalence theorem Mark J. Gotay; James M. Nester — 1979 Annales de l'I.H.P. Physique théorique
Presymplectic lagrangian systems. II : the second-order equation problem Mark J. Gotay; James M. Nester — 1980 Annales de l'I.H.P. Physique théorique