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2. Landes, J.L. and Schaffer, D.H. (1979) Proc. Twelfth U.S. National Fracture Mechanics Symposium, ASTM.
3. Milne, I. and Chell, G.G. (1977) Proc. E.C.F. 2, Darmstadt, Germany, p. 116.
4. Milne, I. and Chell, G.G., (1979a) ASTM STP 668 586.