We thank Dr. D.J. Schaefer, Prof. B.F. Chmekla and Prof. K. Schmidt-Rohr for enlightening discussions regarding solid state NMR, and Mr. R.P. Grosso for HTML processing. S.M.A. acknowledges support from the NSF under grants CHE-9403159 and CHE-9625735, and from Biosym/MSI for generously providing visualization software.