On the Variety Generated by Some Monoid of Order Five
Acta Scientiarum Mathematicarum
It is shown that the semigroup variety generated by the monoid A10=a, b : a2 = a, b2 = b, ba = 01
of order five is hereditarily finitely based and contains countably infinitely many subvarieties. In contrast, the monoid variety generated by A10 is shown to contain only eight subvarieties.
Lee, Edmond W. H., "On the Variety Generated by Some Monoid of Order Five" (2008). Mathematics Faculty Articles. 158.