1. W. F. Brown and J. E. Strawly, ASTM STP 410 (American Society for Testing and Materials, Philadelphia, 1966).
2. D. Broek, “Elementary engineering fracture mechanics, 3rd Edn, (Martinus Nijhoff, Leiden 1982).
3. F. C. Allen, ASTM STP 486 (American Society for Testing and Materials, Philadelphia, 1971) 16.
4. V. Weiss and S. Yukawa, ASTM STP 381 (American Society for Testing and Materials, Philadelphia, 1965) 1.
5. R. H. Christensen and P. H. Denke, ASD-TR-61-207 (1961).