%0 Journal Article
%A Christopher B. Croke
%T Rigidity for surfaces of non-positive curvature.
%J Commentarii mathematici Helvetici
%D 1990
%P 150-170
%V 65
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/CMH_1990__65_3_140188/
%F CMH_1990__65_3_140188