%0 Journal Article
%A A. A. Borisenko
%T Complete $l$-dimensional surfaces of nonpositive extrinsic curvature in a~Riemannian space
%J Sbornik. Mathematics
%D 1977
%P 485-499
%V 33
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SM_1977_33_4_a2/
%G en
%F SM_1977_33_4_a2