1. P. I. Lamekin and K. G. Predko, Kvantovaya Élektron. (Moscow) 9, 2030 (1982).
2. A. L. Sokolov, Opt. Spektrosk. 83, 1005 (1997) [Opt. Spectrosc. 83, 930 (1997)].
3. V. N. Kuryatov and A. L. Sokolov, Kvantovaya Élektron. (Moscow) 32, 324 (2002).
4. A. M. Bel’skii, T. M. Korneichik, and A. P. Khapalyuk, Spatial Structure of Laser Radiation (Belarus. State University, Minsk, 1982) [in Russian].
5. A. V. Nesterov and V. G. Niziev, J. Phys. D: Appl. Phys. 33, 1817 (2000).