@article{GDZPPN002340534,
title = {Invariant two-forms for geodesic flows.},
journal = {Mathematische Annalen},
volume = {302},
year = {1995},
pages = {677-698},
zbl = {0821.58033},
url = {http://dml.mathdoc.fr/item/GDZPPN002340534}
}
Hammenstädt, Ursula. Invariant two-forms for geodesic flows.. Mathematische Annalen, Tome 302 (1995) pp. 677-698. http://gdmltest.u-ga.fr/item/GDZPPN002340534/