TY  - JOUR
AU  - A.A. Markov
TI  - On finitely generated subsemigroups of a free semigroup.
JO  - Semigroup forum
PY  - 1971
SP  - 251
EP  - 258
VL  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1971__3_133864/
ID  - SF_1971__3_133864
ER  -