@article{VMUMM_2002_5_a8,
     author = {S. A. Polikarpov},
     title = {Periodic billiard trajectories in a uniform gravitational field},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {42--45},
     year = {2002},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2002_5_a8/}
}