REFERENCES
Sreekumar, P. et al.,
Ap.J. 494, 523 (1998).
Kappadath, S.C. et al.
Astron. and Astrophys. Suppl. 120, 691 (1996).
Stecker, F.W. and Salamon, M.H.,
Phys. Rev. Letters 76, 3878 (1996).
Stecker, F.W.,
ApJ 212, 60 (1977).
Hunter, S.D. et al.
ApJ 481, 205 (1997).
Dar, A. and Shaviv, N.J.,
Phys. Rev. Letters 75, 3052 (1995).
Stecker, F.W. and Salamon, M.H.,
ApJ 464, 600 (1996).
Chiang, J. et al.,
ApJ 452, 156 (1995).
Stecker, F.W., Salamon, M.H., and Malkan, M.A.,
ApJ 410, L71 (1993).
Padovani, P. et al.,
MNRAS 260, L21 (1993).
Mücke, A., et al.,
Astron. and Astrophys. Suppl. 120, 541 (1996).
Mattox, J.R., et al.,
ApJ 481, 95 (1997).
Jorstad, S.G. et al., ApJ Suppl., in press,
e-print
astro-ph/0101570 (2001).
Dunlop, J.S. and Peacock, J.A.,
MNRAS 247, 19 (1990).
Thompson, D.J. et al.,
ApJ Suppl. 101, 259 (1995).
Salamon, M.H. and Stecker, F.W.,
ApJ 493, 547 (1998).
Chiang, J. and Mukherjee, R.,
ApJ 493, 547 (1998).
Chiang, J. and Mukherjee, R.,
ApJ 496, 752 (1998).
Mukherjee, R., in Proc. Intl. Symp. on High Energy
Gamma-Ray Astronomy, Heidelberg, in press, e-print
astro-ph/0101301.
Mücke, A. and Pohl, M.,
MNRAS 312, 177 (2000).
McNaron-Brown, K. et al.,
ApJ 451, 575 (1995).
The, L.S., Leising, M.D. and Clayton, D.D.,
ApJ 403, 32 (1993).
Watanabe, K., et al.,
ApJ 516, 285 (1999).
Stecker, F.W., Salamon, M.H. and Done, C., e-print
astro-ph/9912106.
Mushotzky, R.F. et al.,
Nature 404, 459 (2000).
Gilli, R., Salvati, M. and Hasinger, G., e-print
astro-ph/0011341.
McConnell, M.L. et al.,
ApJ 543, 928 (2000).
Stecker, F.W., De Jager, O.C. and Salamon, M.H.,
ApJ Letters 473, L75 (1996).
Fossati, G., et al.,
MNRAS 299, 433 (1998).
Stecker, F.W., De Jager, O.C. and Salamon, M.H.,
ApJ Letters 390, L49 (1992).
Stecker, F.W. and De Jager, O.C.,
Astron. and Astrophys. 334, L85 (1998).
Bhattacharjee, P., Shafi, Q. and Stecker, F.W.,
Phys. Rev. Letters 80, 3698 (1998).