Proof. Since f is an epimorphism and Ker f = {0}, by Theorem 3.11, f is annihi-
lator preserving. Let A,B be two non-empty subsets of L. Assume that A∗ = B∗.
Then clearly f(A∗) = f(B∗). Hence {f(A)}∗ = {f(B)}∗. Conversely, assume that
{f(A)}∗ = {f(B)}∗. Let t ∈ A∗ and b ∈ B. Then t ∧ a = 0 for all a ∈ A. Now,