1. V. Yu. Azarov, R. N. Nurmukhametov, and I. B. Stechkina, Dokl. Akad. Nauk SSSR,259, No. 2, 336?340 (1981).
2. A. M. Sarzhevskii, in: Optics and Spectroscopy [in Russian], No. 1, Moscow-Leningrad (1963), pp. 65?71.
3. N. G. Bakhshiev, Opt. Spektrosk.,13, No. 2, 192?199 (1962).
4. V. Yu. Azarov and R. N. Nurmukhametov, Opt. Spektrosk.,48, No. 4, 770?774 (1980).
5. R. N. Nurmukhametov and V. Yu. Azarov, Opt. Spektrosk.,48, No. 1, 30?33 (1980).