@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/