1. Y. Imai and H. Hirotani, Powder Met., (1961), 359.
2. N. J. Grant and O. Preston, J. of Metals, 9 (1957), 349.
3. K. M. Zwilsky and N. J. Grant, J. of Metals, 9 (1957), 1197.
4. C. G. Goetzel, J. of Metals, 11 (1959), 189.
5. C. G. Goetzel, J. of Metals, 11 (1959), 276.