1. 1) Japan Fine Ceramics Assciation, Home page, “FC industry trend research”, 2010.
2. 2) E. G. Acheson, U. S. Patent No. 492767 (1893);
3. No. 492767 655464 (1898).
4. 3) A. P. Bobrievich, V. A. Kalguzhnyi and G. I. Smirnov, Proc. Acad. Sci. USSR, Sec. Geol. Sci., 115, 1189–1192 (1957).
5. 4) A. N. Winchell and H. Winchell, “Element of Optical Mineralogy”, John Wiley & Sons (1954) pp. 20.