%0 Journal Article
%A Robert Bieri
%A Ross Geoghegan
%T Sigma invariants of direct products of groups
%J Groups, geometry, and dynamics
%D 2010
%P 251-261
%V 4
%N 2
%U http://geodesic.mathdoc.fr/articles/10.4171/ggd/82/
%R 10.4171/ggd/82
%F 10_4171_ggd_82