@article{SM_1997_188_3_a3,
     author = {Ya. B. Vorobets},
     title = {Ergodicity of billiards in polygons},
     journal = {Sbornik. Mathematics},
     pages = {389--434},
     year = {1997},
     volume = {188},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1997_188_3_a3/}
}