@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/