@article{GDZPPN001254308,
title = {A generalization of the bicyclic semigroup.},
journal = {Semigroup forum},
volume = {20},
year = {1980},
pages = {13-26},
zbl = {0449.20062},
url = {http://dml.mathdoc.fr/item/GDZPPN001254308}
}
Adair, C.L. A generalization of the bicyclic semigroup.. Semigroup forum, Tome 20 (1980) pp. 13-26. http://gdmltest.u-ga.fr/item/GDZPPN001254308/