1. B. R. Lawn and T. R. Wilshaw, J. Mater. Sci. 10 (1975) 1049.
2. B. R. Lawn and M. V. Swain, ibid 10 (1975) 113.
3. J. Boussinesq, ?Application des Potentiels a l'Etude de l'Equilibre et du Mouvement des Solides Elastiques? (Gauthier-Villars, Paris, 1885).
4. Discussed in S. P. Timoshenko and J. N. Goodier, ?Theory of Elasticity? (McGraw-Hill, New York, 1970) pp. 398?402.
5. A. A. Griffith, Phil. Trans. Roy. Soc. Lond. A211 (1920) 163.