%0 Journal Article
%A I. I. Tugov
%T Group properties (in the large) of second order partial differential equations
%J Doklady Akademii Nauk
%D 1968
%P 1073-1076
%V 181
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1968_181_5_a11/
%G ru
%F DAN_1968_181_5_a11