@article{SIGMA_2020_16_a118,
     author = {Sean Gasiorek},
     title = {Counting {Collisions} in an $N${-Billiard} {System} {Using} {Angles} {Between} {Collision} {Subspaces}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2020},
     volume = {16},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2020_16_a118/}
}