1. Allen, C. W.: 1973,Astrophysical Quantities, Athlone Press, London, p. 142.
2. Budding, E.: 1977,Astrophys. Space Sci. 47, 459.
3. Chandrasekhar, S.: 1950,Radiative Transfer, Chap. 11, Oxford University Press.
4. Hosokawa, Y.: 1958,Science Reports of Tohoku University, Series I, Vol. XLI, No. 4.
5. Kirbiyik, H. and Smith, R. C.: 1976,Monthly Notices Roy. Astron. Soc. 176, 103.