1. H. Le Chatelier, Bull. Soc. Franc. Minéral. Cryst., 10 (1887) 204.
2. M. L. Keith and O. F. Tuttle, Amer. J. Sci., (1952) 208.
3. M. J. Buerger, Crystal Structure Analysis, Wiley & Sons, New York 1960.
4. R. B. Sosman, The Phases of Silica, Rutgers Univ. Press, New Brunswick/N. J. 1965.
5. G. S. M. Moore, special reprint from Hatfield ICTA-Conf., 1992.