1. C. D. Beacham, ?Fracture, An Advanced Treatise?, Vol. I, edited by H. Liebowitz (Academic Press, New York, 1968) p. 243.
2. G. R. Irwin, University of Illinois TAM Report No. 202.
3. W. F. Brown andJ. E. Srawley, ?Plane Strain Toughness Testing?, STP 410 (ASTM, Philadelphia, 1966).
4. J. I. Bluhm, ?Fracture Mechanics of Aircraft Structures?, edited by H. Liebowitz (AGARD, Neuillysur-Seine, 1974) p. 74.
5. J. E. Srawley andW. F. Brown, ?Fracture Toughness Testing and its Applications?, STP 381 (ASTM, Philadelphia, 1965) p. 142.