@article{GDZPPN001256106,
title = {The groupoid of 0-reduced varieties of Semigroups (n).},
journal = {Semigroup forum},
volume = {26},
year = {1983},
pages = {249-274},
zbl = {0546.20052},
url = {http://dml.mathdoc.fr/item/GDZPPN001256106}
}
Martynova, T.A. The groupoid of 0-reduced varieties of Semigroups (n).. Semigroup forum, Tome 26 (1983) pp. 249-274. http://gdmltest.u-ga.fr/item/GDZPPN001256106/