1. Blokhintzev, D.: The Acoustics of an Inhomogeneous Moving Medium, transi by R.T. Beyer and D. Mintzer. Providence, R.. I.: Brown University 1952. See also J. Acoust. Soc. Amer. 18, 322 (1946).
2. Baker, B.B., and E.T. Copson: The Mathematical Theory of Huygens’ Principle, 2nd. ed. London: Oxford University Press 1950.
3. Borgnis, F.E.: Rev. Mod. Phys. 25, 653 (1953).
4. Bouwkamp, C. J.: Thesis, Groeningen, 1941.
5. Bouwkamp, C. J.: Rep. Progr. Phys. 17, 35 (1954).