1. L. H. Aller and S. J. Czyzak, Astrophys. Space Sci. 62, 397 (1979).
2. L. H. Aller and S. J. Czyzak, Astrophys. J. Suppl. Ser. 51, 211 (1983).
3. L. Aller and U. Liller, Nebulae and Interstellar Matter, Ed. by B. Middlehurst and L. Aller (Mir, Moscow, 1966; Univ. of Chicago, Chicago, 1968), p. 30.
4. Z. Brandt, Statistical Methods of Observation Analysis (Mir, Moscow, 1975), p. 312.
5. K. V. Bychkov and A. F. Kholtygin, Elementary Processes in Astrophysical Plasma (Gos.Aastron. Inst. MGU, Moscow, 2007), p. 186.