%0 Journal Article
%A A. A. Borisenko
%T On extremal properties of compact surfaces on nonpositive extrinsic curvature
%J Doklady Akademii Nauk
%D 1987
%P 265-268
%V 294
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1987_294_2_a0/
%G ru
%F DAN_1987_294_2_a0