1. a) Smith, J. O.: Univ. Illinois Engng. Exp. Stat. Bull. No. 334 (1942).
2. Gough, H. J., H. V. Pollard and W. J. Clenshaw: Aeron. Res. Council Rep. and Mem. No. 2522 (1951).
3. Findley, W. N.: Nat. Adv. Comm. Aeron. Tech. Note No. 2924 (1952).
4. Marin, J.: Int. Conference on Fatigue of Metals, London Session 2, Paper 12 (1956).
5. Clark, D. S., and D. S. Woon: Proc. Amer. Soc. Test. Mater. 49, 717 (1949); 53, 755 (1953).