TY  - JOUR
AU  - M. Breen
TI  - Covering in the set of principal ideals in the semigroup of binary relations.
JO  - Semigroup forum
PY  - 1994
SP  - 369
EP  - 376
VL  - 48
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1994__48_3_135325/
ID  - SF_1994__48_3_135325
ER  -