%0 Journal Article
%A M. A. Lavrent'ev
%A B. V. Shabat
%T The geometric properties of solutions of non-linear systems of partial differential equations
%J Doklady Akademii Nauk
%D 1957
%P 810-811
%V 112
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1957_112_5_a6/
%G ru
%F DAN_1957_112_5_a6