Corcoran M.F., R. Petre, J.H. Swank, S.A. Drake, K. Koyama, Y. Tsuboi, R. Viotti, A. Damineli, K. Davidson, K. Ishibashi, and S. White, The Astrophysical Journal494, 381-395(1998).
Ishibashi K., T.R. Gull, K. Davidson, N. Smith, T. Lanz, D.J. Lindler, J.K. Feggans, E. Verner, B.E. Woodgate, R.A. Kimble, and C.W. Bowers, The Astronomical Journal125, 3222-3236(2003).
and 
