Periodic orbits in the case of a zero eigenvalue

Petre Birtea; Mircea Puta; Răzvan Micu Tudoran

Comptes Rendus. Mathématique, Volume 344 (2007) no. 12 p. 779-784

On Ishii's equation

Petre Birtea; Mircea Puta

Comptes Rendus. Mathématique, Volume 341 (2005) no. 2 p. 107-111