1. For the theory of radiative equilibrium, the fundamental paper is K.Schwarzschild, Göttinger Nachrichten, p. 41 (1906).
2. K. Schwarzschild, Berlin Sitzber, p. 1183 (1914).
3. A. S. Eddington, M N 77, p. 16 (1916); Z f Phys7, p. 351 (1921).
4. J. H. Jeans, M N 78, p. 28 (1917); 86, p. 574 (1926).
5. E. A. Milne, MN81, p$1361 (1921); 81, p$1375 (1921); 81, p$1510 (1921);