A counterexample to a Voronoi region conjecture

Given a 2D-symmetric lattice /spl Lambda/, it was conjectured by Forney (1989) that the projection of the Voronoi region R(/spl Lambda/) onto two coordinates equals the Voronoi region of the constituent 2D-sublattice /spl Lambda//spl nu//sub 2/. We present a three-dimensional counterexample. >