%0 Journal Article
%A V. S. Vinogradov
%T The geometric meaning of the condition of ellipticity of a system of first order differential equations in the plane and its reduction to a complex special form
%J Doklady Akademii Nauk
%D 1981
%P 1043-1046
%V 260
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1981_260_5_a3/
%G ru
%F DAN_1981_260_5_a3