An estimate on the relative Morse index for strongly indefinite functionals. Abbondandolo, A.; Felmer, P.; Molina, J. — 2001 Electronic Journal of Differential Equations (EJDE) [electronic only]
Heteroclinic orbits for spatially periodic hamiltonian systems P. L. Felmer — 1991 Annales de l'I.H.P. Analyse non linéaire
A Liouville-type theorem for elliptic systems D. G. De Figueiredo; P. L. Felmer — 1994 Annali della Scuola Normale Superiore di Pisa - Classe di Scienze