Planar Sublattices of a Free Lattice. I
Planar Sublattices of a Free Lattice. I
There are three lattice-theoretic properties that are generally used to open a discussion on sublattices of a free lattice: ( W ) for all a, b, c, d, a Λ b ≦ c V d implies a A b ≦ c, a Λ b g rf, a ≦ cVd,orb ≦ …