1. C. Bender and S. Orszag, Advanced Mathematical Methods for Scientists and Engineen (McGraw‐Hill, New York, 1978).
2. A. Z. Botros and S. F. Mahmoud, Radio Sci. 13, 379 (1978).RASCAD0048-6604
3. L. Cagniard, Reflection and Refraclion of Progressive Seismic Waves (McGraw‐Hill, New York, 1962).
4. A. T. De Hoop and H. J. Frankena, Appl. Sci. Res. B 8, 369 (1960).
5. H. J. Frankena, Appl. Sci. Res. 8, 357 (1960).