1. R. Burridge and H. Weinberg, Chapter III, this volume.
2. C. Wilcox, Spectral analysis of the Laplacian with a discontinuous coefficient in a half space and the associated eigenfunction expansion. Also, Transient acoustic wave propagation in a symmetric Epstein duct. University of Utah reports, January 1973 and May 1974.
3. W. H. Munk, Sound channel in an exponentially stratified ocean, with application to SOFAR, J. Acoust. Soc. Am. 55, (1974), p. 220.
4. F. D. Tappert, Chapter V, this volume.
5. Probabilistic methods in Applied Math.;U. Frisch,1968