%0 Journal Article
%A V. F. Lazutkin
%T The existence of caustics for a~billiard problem in a~convex domain
%J Izvestiya. Mathematics 
%D 1973
%P 185-214
%V 7
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IM2_1973_7_1_a8/
%G en
%F IM2_1973_7_1_a8