@article{GDZPPN002441977, title = {Convex billiards and a theorem by E. Hops.}, journal = {Mathematische Zeitschrift}, volume = {212}, year = {1993}, pages = {147-154}, zbl = {0790.58023}, url = {http://dml.mathdoc.fr/item/GDZPPN002441977} }
Bialy, Misha. Convex billiards and a theorem by E. Hops.. Mathematische Zeitschrift, Tome 212 (1993) pp. 147-154. http://gdmltest.u-ga.fr/item/GDZPPN002441977/