1. B. E. Warren, H. Krutter, and O. Morningstar, J. Am. Ceram. Soc. 19, 202 (1936).JACTAW0002-7820
2. J. Zarzycki, Non‐Crystalline‐Solids, V. D. Fréchette, Ed. (John Wiley & Sons, Inc., New York, 1960), p. 117.
3. R. W. James, The Optical Principles of the Diffraction of X‐Rays (G. Bell & Sons, London, 1954), p. 505.
4. J. Waser and V. Schomaker, Rev. Mod. Phys. 25, 671 (1953); RMPHAT0034-6861
5. see particularly pp. 680–681.