@article{SM_1971_15_4_a3,
     author = {G. A. Margulis},
     title = {On the action of unipotent groups in a~lattice space},
     journal = {Sbornik. Mathematics},
     pages = {549--554},
     year = {1971},
     volume = {15},
     number = {4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1971_15_4_a3/}
}