Aromaticity rules for cycles with arbitrary numbers of half-twists

A simple proof is given that the Hückel aromaticity rules generalise to cycles with an arbitrary number of half-twists, T; addition/removal of half-twists two at a time preserves all eigenvalues and degeneracies, so that closed-shell aromatic systems occur at pi-electron counts 4N+ 2, and antiaromatic at 4N for even T, and vice versa for odd T.