1. 1) A. M. Turkalo: Trans. AIME, 218 (1960), 24.
2. 2) D. Hardwick and K. R. Pirt: J. Iron Steel Inst., 196 (1960), 301;
3. B. Cina and P. Jubb: J. Iron Steel Inst., 193 (1959), 329;
4. R. M. Fisher et al.: Trans. AIME, 191 (1951), 1064.
5. 3) To be published.