@article{DAN_1961_136_4_a2,
     author = {B. M. Gurevich},
     title = {The entropy of horocycle flows},
     journal = {Doklady Akademii Nauk},
     pages = {768--770},
     publisher = {mathdoc},
     volume = {136},
     number = {4},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_136_4_a2/}
}