1. Yu. A. Anan’ev, Optical Resonators and Laser Beams (Nauka, Moscow, 1990) [in Russian].
2. V. M. Babich and V. S. Buldyrev, Asymptotic Methods in Short-Wavelength Diffraction Theory (Nauka, Moscow, 1973; Alpha Science, Oxford, 2007).
3. V. N. Kudashov, A. B. Plachenov, and A. M. Radin, Opt. Spektrosk., 88(1), 130 (2000) [Opt. Spectrosc. 88, 118 (2000)].
4. M. M. Popov, Opt. Spektrosk. 25, 314 (1968) [Opt. Spectrosc. 25, 213 (1968)]
5. M. M. Popov, Vestn. Leningr Univ., Ser. 4: Fiz. Khim., 22(4), 42 (1969).