1. D. A. Ryder and A. C. Smale, ?Fracture of Solids?, edited by D. C. Drucker and J. J. Gilman (Interscience, New York, 1963) p. 237.
2. T. Kawabata and O. Izumi, Acta- Metall. 24 (1976) 817.
3. A. J. Sedriks, P. W. Slattery and E. N. Pugh, Trans. ASM 62 (1969) 238, 815.
4. P. N. T. Unwin and G. C. Smith, J. Inst. Met. 97 (1969) 299.
5. N. Ryum and K. Baardeth, ibid. 96 (1968) 92.