Geodesic
The Lattice of Equational Classes of Semigroups with Zero
Canadian mathematical bulletin, Tome 14 (1971) no. 4, pp. 531-534

Voir la notice de l'article provenant de la source Cambridge University Press

In contrast to the very complicated structure of the lattice of equational classes of commutative semigroups (see [5]), the lattice of equational classes of commutative monoids (semigroups with unit) is isomorphic with N × N* with a unit adjoined, where N is the lattice of natural numbers with the usual order and N* is the lattice of natural numbers ordered by division. (See [4].) However, the lattice of equational classes of commutative semigroups-with-zero is not so simple to describe. 
Nelson, Evelyn. The Lattice of Equational Classes of Semigroups with Zero. Canadian mathematical bulletin, Tome 14 (1971) no. 4, pp. 531-534. doi: 10.4153/CMB-1971-094-3
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[1] 1. Burris, S. and Nelson, E., Embedding the dual of ∏ in the lattice of equational classes of commutative semigroups, Proc. Amer. Math. Soc. (to appear). Google Scholar

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[5] 5. Nelson, E., The lattice of equational classes of commutative semigroups, Canad. J. Math, (to appear). Google Scholar

[6] 6. Sachs, D., Identities in finite partition lattices, Proc. Amer. Math. Soc. 12 (1969), 944-945. Google Scholar

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