1. K. T. Compton, “Some properties of resonance radiation and excited atoms,” Philos. Mag. 45, 750–760 (1923).
2. E. A. Milne, “The diffusion of imprisoned radiation through a gas,” J. London Math. Soc. 1, 40–51 (1926).
3. V. V. Sobolev, “On the theory of the non-stationary radiation field,” Astron. Zh. 29, 406–414, 517–525 (1952).
4. V. V. Sobolev, A Treatise on Radiative Transfer (Gostekhizdat, Moscow, 1956; Van Nostrand, Princeton, NJ, 1963).
5. K. M. Case and P. F. Zweifel, Linear Transport Theory (Addison-Wesley, Reading, MA, 1967).