@article{GDZPPN002230593,
title = {Subharmonics near an equilibrium point for Hamiltonian systems.},
journal = {Manuscripta mathematica},
volume = {67},
year = {1990},
pages = {359-396},
zbl = {0688.34027},
url = {http://dml.mathdoc.fr/item/GDZPPN002230593}
}
Felmer, Patricio L. Subharmonics near an equilibrium point for Hamiltonian systems.. Manuscripta mathematica, Tome 67 (1990) pp. 359-396. http://gdmltest.u-ga.fr/item/GDZPPN002230593/