%0 Journal Article
%A I. E. Pleshchinskaya
%T The equivalence of some classes of first-order elliptic and hyperbolic systems and second-order partial differential equations
%J Differencialʹnye uravneniâ
%D 1987
%P 1634-1637
%V 23
%N 9
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1987_23_9_a23/
%G ru
%F DE_1987_23_9_a23