1. A.K. Mal and L. Knopoff, J. Inst. Math. Applics., 3, 376 (1967).
2. A.K. Mal and C.C. Yin, Development in Geotechnical Engineering, Vol. 44, ed. A.S. Cakmak, (1987), p. 107.
3. J.A. Hudson and J.R. Heritage, Geophys. J.R. Astr. Soc., 66, 221 (1981).
4. J.K. Lee and A.K. Mal, Applied Mathematics and Computation (accepted).
5. J.K. Lee and A.K. Mal, Review of Progress in Quantitative Nondestructive Evaluation, eds. D.O. Thompson and D.E. Chimenti, Vol. 12, (1993), p. 1751.