P. Jovanović, and L. Č. Popović. (2009)cite arxiv:0903.0978
Comment: 62 pages, 24 figures, to appear as a chapter of the book "Black
Holes: Properties, Formation and Features" (to be published by Nova Science
Publishers, Inc).
M. Park, and J. Ostriker. (1998)cite arxiv:astro-ph/9811048
Comment: Figs 1 and 2 replaced with corrected figures. 9 pages, 3 Postscript
figures. Plain tex. Review talk presented at 31st COSPAR meeting (1996).
Revised version will appear in Adv. in Space Research.