@article{GDZPPN002405474,
title = {Schreier Varieties of Semigroups.},
journal = {Mathematische Zeitschrift},
volume = {111},
year = {1969},
pages = {296-299},
zbl = {0175.29301},
url = {http://dml.mathdoc.fr/item/GDZPPN002405474}
}
Evans, Trevor. Schreier Varieties of Semigroups.. Mathematische Zeitschrift, Tome 111 (1969) pp. 296-299. http://gdmltest.u-ga.fr/item/GDZPPN002405474/