Variational calculus in several variables : a hamiltonian approach A. Echeverría Enríquez; M. C. Muñoz Lecanda — 1992 Annales de l'I.H.P. Physique théorique
Lagrangian theory for presymplectic systems M. C. Muñoz Lecanda; N. Roman Roy — 1992 Annales de l'I.H.P. Physique théorique