1. Lange, F.F. and Lambe, K.A.D. Phil. Mag. 18, 129, (1968).
2. Post, D. Proc. Soc. Exp. Stress Anal. 12, 99, (1954).
3. Rothman, M. and Ross, D.S. Engineering 179, 175, (1955).
4. Frocht, M.M. Photoelasticity Vol. 1, p. 198, John Wiley, (1941).
5. Williams, M.L. J. Appl. Mech. 24, 109, (1957).