1. V. V. Antsiferov, K. G. Folin, V. S. Pivtsov, and V. D. Ugozhaev, Zh. Tekh. Fiz.,41, 2594 (1971).
2. V. V. Antsiferov, V. S. Pivtsov, V. D. Ugozhaev, and K. G. Folin, Kvant. Élektron. No. 3 (15), 57 (1973).
3. N. S. Belokrinitskii, A. D. Manul'skii, and M. S. Soskin, Ukr. Fiz. Zh.,12, 1720 (1967).
4. W. H. Keene and J. A. Weiss, Appl. Opt.,3, 545 (1964).
5. K. G. Folin, V. D. Ugozhaev, V. V. Antsiferov, and B. V. Anikeev, Zh. Éksp. Teor. Fiz.,58, 1146 (1970).