%0 Journal Article
%A Edward J. Tully
%T Expletives in languages and middle units in semigroups.
%J Semigroup forum
%D 1989
%P 77-84
%V 38
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SF_1989__38_2_134942/
%F SF_1989__38_2_134942