Erratum

The cover caption for the issue of 9 February 1990 should have described the molecule on the cover as VPI-5 (Dow and Virginia Polytechnic Institute), not as ALPO-5 (Union Carbide). The first sentence of the caption should have read, "Superlattices of p-nitroaniline molecules self-assemble and orient within the polar, greater than 10 angstrom wide channels of VIP-5, a molecular sieve." The preferred orientation of the polar molecules occurs in both materials.