%0 Journal Article
%A Th. Friedrich
%T On an equality for 3-dimensional manifolds
%J Commentationes Mathematicae
%D 1975
%P  187-188
%V 18
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/articles/10.14708/cm.v18i2.5820/
%R 10.14708/cm.v18i2.5820
%G pl
%F 10_14708_cm_v18i2_5820