@article{GDZPPN002082993, title = {Geometrical Aspects of the Circular Billiard Problem.}, journal = {Elemente der Mathematik}, volume = {47}, year = {1992}, pages = {114-117}, zbl = {0800.70052}, url = {http://dml.mathdoc.fr/item/GDZPPN002082993} }
Hungerbühler, Norbert. Geometrical Aspects of the Circular Billiard Problem.. Elemente der Mathematik, Tome 47 (1992) pp. 114-117. http://gdmltest.u-ga.fr/item/GDZPPN002082993/