TY  - JOUR
AU  - R.D. Kopperman
TI  - Lengths on semigroups and groups.
JO  - Semigroup forum
PY  - 1982
SP  - 345
EP  - 360
VL  - 25
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1982__25_134584/
ID  - SF_1982__25_134584
ER  -