@article{GDZPPN002438577,
title = {Action-angle coordinates at singularities for analytic integrable systems.},
journal = {Mathematische Zeitschrift},
volume = {207},
year = {1991},
pages = {363-408},
zbl = {0707.58026},
url = {http://dml.mathdoc.fr/item/GDZPPN002438577}
}
Ito, Hidekazu. Action-angle coordinates at singularities for analytic integrable systems.. Mathematische Zeitschrift, Tome 207 (1991) pp. 363-408. http://gdmltest.u-ga.fr/item/GDZPPN002438577/