@article{GDZPPN00210976X, title = {The K-property of N billiard balls I.}, journal = {Inventiones mathematicae}, volume = {110}, year = {1992}, pages = {521-548}, zbl = {0759.58029}, url = {http://dml.mathdoc.fr/item/GDZPPN00210976X} }
Simányi, Nándor. The K-property of N billiard balls I.. Inventiones mathematicae, Tome 110 (1992) pp. 521-548. http://gdmltest.u-ga.fr/item/GDZPPN00210976X/