@article{GDZPPN002091402,
title = {A Bound for the Fixed-Point Index of an Area-Preserving Map with Applications to Mechanics.},
journal = {Inventiones mathematicae},
volume = {27},
year = {1974},
pages = {187-200},
zbl = {0331.55006},
url = {http://dml.mathdoc.fr/item/GDZPPN002091402}
}
Simon, Carl P. A Bound for the Fixed-Point Index of an Area-Preserving Map with Applications to Mechanics.. Inventiones mathematicae, Tome 27 (1974) pp. 187-200. http://gdmltest.u-ga.fr/item/GDZPPN002091402/