%0 Journal Article
%A Graham Hall
%T Some general, algebraic remarks on tensor classification, the group $O(2,2)$ and sectional curvature in 4-dimensional manifolds of neutral signature
%J Colloquium Mathematicum
%D 2017
%P 63-86
%V 150
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/articles/10.4064/cm7140s-3-2017/
%R 10.4064/cm7140s-3-2017
%G en
%F 10_4064_cm7140s_3_2017