@article{MZM_1997_62_1_a6,
     author = {Ya. B. Vorobets},
     title = {Billiards in rational polygons: {Periodic} trajectories, symmetries and $d$-stability},
     journal = {Matemati\v{c}eskie zametki},
     pages = {66--75},
     year = {1997},
     volume = {62},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1997_62_1_a6/}
}