@article{GDZPPN002436876,
title = {On Elliptic Lower Dimensional Tori in Hamiltonian Systems.},
journal = {Mathematische Zeitschrift},
volume = {202},
year = {1989},
pages = {559-608},
zbl = {0662.58037},
url = {http://dml.mathdoc.fr/item/GDZPPN002436876}
}
Pöschel, Jürgen. On Elliptic Lower Dimensional Tori in Hamiltonian Systems.. Mathematische Zeitschrift, Tome 202 (1989) pp. 559-608. http://gdmltest.u-ga.fr/item/GDZPPN002436876/