TY  - JOUR
AU  - A.T. Lisan
TI  - Ultrafilters on a discrete set with two binary operations.
JO  - Semigroup forum
PY  - 1991
SP  - 77
EP  - 82
VL  - 43
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1991__43_3_135097/
ID  - SF_1991__43_3_135097
ER  -