@article{SM_2020_211_7_a4,
     author = {I. F. Kobtsev},
     title = {An elliptic billiard in a~potential force field: classification of motions, topological analysis},
     journal = {Sbornik. Mathematics},
     pages = {987--1013},
     publisher = {mathdoc},
     volume = {211},
     number = {7},
     year = {2020},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2020_211_7_a4/}
}