1. R. A. Hadfield:Metallurgy and Its Influence on Modem Progress, p. 91, Chapman and Hall Ltd., London, 1925.
2. ASTM A 128-75a,Annual Book of ASTM Standards, Part 2, p. 95, ASTM,, Philadelphia, PA, 1979.
3. E. R. Hall:ASM Technical Report No. C6-17.1, p. 15, 1966.
4. D. E. Diesburg and F. Borik:Symposium on Materials for the Mining Industry, p. 15, Climax Molybdenum Company, Greenwich, CN, 1974.
5. R. W. Cahn:The Encyclopedia of Ignorance, p. 140, Pergamon Press, NY, 1977.