%0 Journal Article
%A A. A. Borisenko
%T Surfaces of nonpositive extrinsic curvature in spaces of constant curvature
%J Sbornik. Mathematics
%D 1982
%P 297-310
%V 42
%N 3
%U http://geodesic.mathdoc.fr/item/SM_1982_42_3_a0/
%G en
%F SM_1982_42_3_a0