@article{FPM_2019_22_6_a8,
     author = {S. E. Pustovoytov},
     title = {Topological analysis of a~billiard in elliptic ring in a~potential field},
     journal = {Fundamentalʹna\^a i prikladna\^a matematika},
     pages = {201--225},
     publisher = {mathdoc},
     volume = {22},
     number = {6},
     year = {2019},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FPM_2019_22_6_a8/}
}