@article{GDZPPN002103982,
title = {Rigid reparametrizations and cohomology for horocycle flows.},
journal = {Inventiones mathematicae},
volume = {88},
year = {1987},
pages = {341-374},
zbl = {0697.58046},
url = {http://dml.mathdoc.fr/item/GDZPPN002103982}
}
Ratner, M. Rigid reparametrizations and cohomology for horocycle flows.. Inventiones mathematicae, Tome 88 (1987) pp. 341-374. http://gdmltest.u-ga.fr/item/GDZPPN002103982/