%0 Journal Article
%A H.J. Shyr
%T Every subsemigroup of a free semigroup with zero is not an R-semigroup.
%J Semigroup forum
%D 1976
%P 380-382
%V 12
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SF_1976__12_134189/
%F SF_1976__12_134189