1. Bush, I. V., J. Franklin Inst., 212, 447 (1931). See also Hartree, D. R., Math. Gaz., 22, 342 (1938); Proc. Roy. Inst., 31, 151 (1940); and Nature, 146, 319 (1940).
2. Beuken, L., Econ. Tech. Tijdschrift (Maastricht) ige jaarg., 43 (1939); Paschkis, V., and Baker, H. D., Heat Treatment and Forging, 27, 375 (1941), and Trans. Amer. Soc. Mech. Eng., 64, 105 (1942). See also Jackson, R., and others, J. Iron and Steel Inst., Part II of 1944, p. 211.