%0 Journal Article
%A I. Yu. Ryzhakov
%T The problem of finding the characteristic set in certain special cases
%J Izvestiâ vysših učebnyh zavedenij. Matematika
%D 1968
%P 63-72
%N 8
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IVM_1968_8_a8/
%G ru
%F IVM_1968_8_a8