variety; lattice; compact element
We prove that the lattice of varieties contains almost no compact elements.
 J. Ježek: The lattice of equational theories
. Czechoslovak Math. J. 31 (1981), 127–152; 573–603. MR 0604120
 R. McKenzie, G. McNulty, W. Taylor: Algebras, Lattices, Varieties, Vol. I
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