@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/