%0 Journal Article
%A V. M. Petkov
%T Necessary conditions for correctness of the Cauchy problem for nonstrictly hyperbolic equations
%J Doklady Akademii Nauk
%D 1972
%P 287-290
%V 206
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1972_206_2_a6/
%G ru
%F DAN_1972_206_2_a6