@article{SM_1969_7_4_a7,
     author = {\`E. B. Vinberg},
     title = {Some examples of crystallographic groups in {Lobachevskii} spaces},
     journal = {Sbornik. Mathematics},
     pages = {617--622},
     year = {1969},
     volume = {7},
     number = {4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1969_7_4_a7/}
}