%0 Journal Article
%A R.D. Kopperman
%T Lengths on semigroups and groups.
%J Semigroup forum
%D 1982
%P 345-360
%V 25
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SF_1982__25_134584/
%F SF_1982__25_134584