| Sumario: | A Q-distributive lattice is an algebra (L, ∨, ∧, ∇, 0, 1) of type (2, 2, 1, 0, 0) such that (L, ∨, ∧, 0, 1) is a bounded distributive lattice and ∇ satisfies the equations ∇0 = 0, x ∧ ∇x = x, ∇(x ∨ y) = ∇x ∨ ∇y and ∇(x ∧ ∇y) = ∇x ∧ ∇y. The aim of this paper is to find, for each proper subvariety of the variety of Q-distributive lattices, an equation which determines it, relatively to the whole variety, as well as to give a characterization of the minimum number of variables needed in such equation.
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