1. R. D. Mindlin, J. App. Mech. 8, A187 (1941).
2. D. C. Drucker and R. D. Mindlin, J. App. Phys. 11, 724 (1940).
3. L. N. G. Coker and E. G. Filon, A Treatise on Photo-Elasticity (Cambridge University Press, Teddington, 1931), Chap. I.
4. See reference 3, p. 198, Eq. (3.102).
5. F. E. Neumann, Abh. d. Kön. Akad. d. Wissenschaften zu Berlin (1841) Part II, p. 1.