@article{RM_1992_47_3_a1,
     author = {Ya. B. Vorobets and G. A. Gal'perin and A. M. Stepin},
     title = {Periodic billiard trajectories in polygons: generating mechanisms},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {5--80},
     publisher = {mathdoc},
     volume = {47},
     number = {3},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1992_47_3_a1/}
}