1. K.W. Stalker, C. Clark, J.A. Ford, F.M. Richmond, and J. R. Stephens:Metals Progress, Oct. 1984, pp. 55-65.
2. A. S. Jameson, A. D. Ellis, and G. F. Meyer:The Iron Age, April 1951, pp. 102-06.
3. D. V. Gullotti, J. L. Hurley, and C. H. Shelton:Metals Progress, Nov. 1965, pp. 2-4.
4. C. V. Darragh, J. J. Donze, and C. P. Weigel:Metals Progress, Dec. 1971, pp. 74-75.
5. Czech patent PV8368-68, 1969.