%0 Journal Article
%A A.T. Lisan
%T Ultrafilters on a discrete set with two binary operations.
%J Semigroup forum
%D 1991
%P 77-82
%V 43
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SF_1991__43_3_135097/
%F SF_1991__43_3_135097