1. Busbridge, I. W. and Stibbs, D. W. N.: 1954,Monthly Notices Roy. Astron. Soc. 114, 2.
2. Das Gupta, S. R.: 1956,Sci. Cult. 22, 177.
3. Sobolev, V. V.: 1951,Astron. J. 28, Bulletin 5.
4. Sobolev, V. V.: 1963,A Treatise on Radiative Transfer (Eng. transl. by S. I. Gaposchkin), D. Van Nostrand Co.
5. Woolley, R. v. d. R. and Stibbs, D. W. N.: 1953,The Outer Layers of a Star, Oxford Univ. Press.