1. L. M. Biberman, Zh. Éksp. Teor. Fiz. 17, 416 (1947).
2. T. Holstein, Phys. Rev. 72, 1212 (1947).
3. V. V. Sobolev, Radiation Energy Transfer in Stellar and Planetary Atmospheres (Gostekhizdat, Moscow, 1965) [in Russian].
4. V. V. Ivanov, Radiation Transfer and Spectra of Heavenly Bodies (Nauka, Moscow, 1969) [in Russian].
5. D. Mikhalas, Stellar Atmospheres (Mir, Moscow, 1982) [in Russian].