Definition 1. An algebra (A,⊕,∗ , 0) with a binary operation ⊕ : A×A → A and with a unary operation ∗ : A → A and a constant 0, is said to be an MV -algebra iff satisfies the following conditions for all a, b, c ∈ A: (1) (A,⊕, 0) is a commutative monoid; (2) x⊕ 0∗ = 0∗ for every x ∈ A; (3) (x∗)∗ = x for every x ∈ A; (4) (x∗ ⊕ y)∗ ⊕ y = (x⊕ y∗)∗ ⊕ x for every x, y ∈ A. ¿From (4), setting y = 0∗,...