School of Mathematics and Statistics, Lanzhou University, Lanzhou, Gansu 730000, P.R. China

*e-mail:* `lijr@lzu.edu.cn`

**Abstract.**
It is known that the variety *M _{n}* generated by all monoids of order

**2010 Mathematics Subject Classification.**
20M07.

**Key words and phrases.** Monoid, semigroup, variety, finitely based.

DOI: 10.3336/gm.50.2.08

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