%0 Journal Article
%A P. Ehrlich
%T Null cones and pseudo-riemannian metrics.
%J Semigroup forum
%D 1991
%P 337-343
%V 43
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SF_1991__43_3_135120/
%F SF_1991__43_3_135120