Arav N., K.T. Korista, M. de Kool, V.T. Junkkarinen, and M.C. Begelman, The Astrophysical Journal 516, 27-46 (1999).
Burks G.S., F. Bartko, J.M. Shull, J.T. Stocke, E.R. Sachs, M. Burbidge, R.D. Cohen, V.T. Junkkarinen, R.J. Harms, and D. Massa, The Astrophysical Journal 437, 630 (1994).
and 
