%0 Journal Article
%A I. Tabov
%A D. Kolev
%T Obstacles to the propagation of simple waves in a nonhomogeneous medium
%J Differencialʹnye uravneniâ
%D 1999
%P 570-572
%V 35
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1999_35_4_a17/
%G ru
%F DE_1999_35_4_a17