1. US Patent No. 3,356,542.
2. G. D. Smith and D. H. Yates:Metals Progr., 1968, vol. 93, pp. 100–02.
3. A. C. Hood:Metals Progr., 1968, vol. 93, pp. 81–84.
4. A. Giamei, J. Burma, and E. J. Freise:Cobalt, 1968, no. 39, pp. 88–96.
5. F. R. Morral:J. Metals, 1968, vol. 20, pp. 52–59.