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2. R. J. Bucci, W. G. Clark and P. C. Paris, Stress Analysis and Growth of Cracks, Part I, ASTM-STP 513,p. 177. American Society for Testing Materials(1972).
3. R. J. Bucci, P. C. Paris, R. W. Hertzberg, R. A. Schmidt and A. F. Anderson, Stress Analysis and Growth of' Cracks, Part I, ASTM-STP 513,p. 125. American Society for Testing Materials(1972).