1. J.M. Coffey, in The Measurement of Crack Length and Shape During Fracture and Fatigue, edited by C. J. Beevers ( Chameleon Press, Ltd., London, 1980 ) p. 345.
2. O. Buck and B. R. Tittman, in Advances in Crack Length Measurement, edited by C. J. Beevers ( Chameleon Press, Ltd., London, 1982 ) p. 413.
3. O. Buck, in Fracture Mechanics: Microstructure and Micromechanisms, edited by S. V. Nair, J. K. Tien, R. C. Bates and O. Buck ( American Society for Metals, Metals Park, OH, 1987 ) p. 31.
4. R. F. Lumb, R. J. Hudgell and P. Winship, in Proceedings 7th International Conference on NDT, Paper H-01, Warsaw, 1973.
5. M. G. Silk, in Research Techniques in Nondestructive Testing, Vol. 3, Academic Press, London and New York, 1977, p. 51.