TY  - JOUR
AU  - C.C. Edmunds
TI  - Varieties generated by semigroups of order four.
JO  - Semigroup forum
PY  - 1980
SP  - 67
EP  - 82
VL  - 21
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1980__21_134435/
ID  - SF_1980__21_134435
ER  -