%0 Journal Article
%A L. Nirenberg
%A F. Trèves
%T On local solvability of linear partial differential equations. I. Necessary conditions
%J Matematika
%D 1971
%P 142-172
%V 15
%N 3
%U http://geodesic.mathdoc.fr/item/MAT_1971_15_3_a5/
%G ru
%F MAT_1971_15_3_a5