1. L. B. Felsen, N. Marcuvitz: Radiation and Scattering of Waves (Prentice Hall, Inc., Englewood Cliffs, N. J. 1973)
2. Reference 1.1, Sect. 1.5b
3. M. Kline, I. W. Kay: Electromagnetic Theory and Geometrical Optics (Interscience Publishers, Wiley and Sons, New York 1965) Sect. 1.3
4. Reference 1.1, Sects. 1.1b and 1.1c
5. Yu. A. Kravtsov, L. A. Ostrovsky, N. S. Stepanov: Proc. IEEE 62, 1492 (1974)