1. Meyer, E., Z. VDI, 52, 645, 740, 835 (1908).
2. O'Neill, H., “The Hardness of Metals and its Measurements” (London, 1934).
3. Finniston, H. M., Jones, E. R. W., and Madsen, P. E., Nature, 164, 1128 (1949).
4. Taylor, G. I., Proc. Roy. Soc., A, 145, 388 (1934). Seitz, F., “Physics of Metals”, 85 (McGraw-Hill, 1943).
5. Tabor, D., Proc. Roy. Soc., A, 192, 247 (1948).