1. C. S. Hurlbut Jr, ?Dana's Manual of Mineralogy? (John Wiley, New York, 1970) pp. 414, 420.
2. E. H. Kraus, W. F. Junt, andL. S. Ramsdell, ?Mineralogy, An Introduction to the Study of Minerals and Crystals? (McGraw-Hill, New York, 1959) p. 388, 392.
3. R. C. Bradt, R. E. Newham andJ. V. Biggers,Am. Mineralogists,58 (1973) 727?732.
4. D. J. Rowcliffe andV. Fruhauff,J. Mater. Sci. 12 (1977) 35?42.
5. H. J. Mcskimin J. Acoust. Soc. Am.,33 (1961) 12?16.