1. W. Rosner, G. Wunner, H. Herold, and H. Ruder, J. Phys. B, 17, 29 (1984).
2. S. Jordan, Astron. Astrophys., 265, 570 (1992).
3. D. T. Wickramasinghe and L. Ferrario, Publ. Astron. Soc. Pacific, 112, 873 (2000).
4. V. V. Zheleznyakov, Radiation in Astrophysical Plasmas [in Russian], Yanus-K, Moscow (1997).
5. V. V. Zheleznyakov, S. A. Koryagin, and A. V. Serber, Astron. Lett., 25, No. 7, 437 (1999).