@article{GDZPPN002090384,
title = {Normal Modes for Nonlinear Hamiltonian Systems.},
journal = {Inventiones mathematicae},
volume = {20},
year = {1973},
pages = {47-58},
zbl = {0264.70020},
url = {http://dml.mathdoc.fr/item/GDZPPN002090384}
}
Weinstein, Alan. Normal Modes for Nonlinear Hamiltonian Systems.. Inventiones mathematicae, Tome 20 (1973) pp. 47-58. http://gdmltest.u-ga.fr/item/GDZPPN002090384/