%0 Journal Article
%A V. E. Balabaev
%T The Ellipticity Problem for Systems of First-Order Partial Differential Equations
%J Differencialʹnye uravneniâ
%D 2002
%P 411-413
%V 38
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_2002_38_3_a17/
%G ru
%F DE_2002_38_3_a17