TY  - JOUR
AU  - Lai, C. K.
AU  - Shum, Kar-Ping
TI  - Characterizations of dual semigroups
JO  - Czechoslovak Mathematical Journal
PY  - 1989
SP  - 578
EP  - 584
VL  - 39
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1989.102330/
DO  - 10.21136/CMJ.1989.102330
LA  - en
ID  - 10_21136_CMJ_1989_102330
ER  -