1. H. Hertz,J. Reine Angew. Math. 92 (1881) 156; translated and reprinted in English in ?Hertz's Miscellaneous Papers? (Macmillan, New York, 1896) Ch. 5.
2. Idem., Verhandlungen des Vereins zur Beforderung des Gewerbe Fleisses 61 (1882) 449; translated and reprinted in English in ?Hertz's Miscellaneous Papers? (Macmillan, New York, 1896) Ch. 6.
3. Auerbach,Ann. Physik (Leipzig) 43 (1891) 61.
4. A. A. Griffith,Phil. Trans. R. Soc. A221 (1920) 163.
5. B. Hamilton andR. Rawson,J. Mech. Phys. Solids 18 (1970) 127.