@article{SM_2021_212_12_a0,
     author = {V. V. Vedyushkina},
     title = {Topological type of isoenergy surfaces of billiard books},
     journal = {Sbornik. Mathematics},
     pages = {1660--1674},
     publisher = {mathdoc},
     volume = {212},
     number = {12},
     year = {2021},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2021_212_12_a0/}
}