1. J. R. Griffiths, I. L. Mogford, and C. E. Richards: Central Electricity Generating Board, England, unpublished research.
2. S. J. Maddox: to be publishedin Metal Construction and Brit. Weld. J.
3. T.R. Gurney:Metal Construction and Brit. Weld. J., 1970, vol. l, p. 91.
4. B. Gross and J. E. Srawley. NASA Tech. Rept. D2603, Jan., 1965.
5. W. F. Brown and J. E. Srawley: Am. Soc. Testing Mater., Spec. Tech. Publ. no. 410,1966, p. 23.