1. 1S. D. Stookey , "Method of Making Ceramics and Products Thereof ," U. S. Pat, 2,920,971, 1960 ; Ceram. Abstr., 1960 , p. 142a .
2. 4Werner Vogel, and Klaus Gerth , "Catalyzed Crystallization in Glass ,"ibid., pp. 11 -22 .
3. 5S. M. Ohlberg, H. R. Golob, and D. W. Strickler , "Crystal Nucleation by Glass in Glass Separation ,"ibid., pp. 55 -62 .