@article{GDZPPN001259822,
title = {On the axiomatic rank of varieties generated by a semigroup or monoid with one defining relation.},
journal = {Semigroup forum},
volume = {38},
year = {1989},
pages = {17-38},
zbl = {0671.20056},
url = {http://dml.mathdoc.fr/item/GDZPPN001259822}
}
Shneerson, L.M. On the axiomatic rank of varieties generated by a semigroup or monoid with one defining relation.. Semigroup forum, Tome 38 (1989) pp. 17-38. http://gdmltest.u-ga.fr/item/GDZPPN001259822/