1. Fishman, G. J. et al. Proc. 2nd Gamma Ray Observatory Science Workshop (in the press).
2. Meegan, C. A. et al. Nature 355, 143–145 (1992).
3. Prilutski, O. F. & Usov, V. V. Astrophys. Space Sci. 34, 395–401 (1975).
4. Usov, V. V. & Chibisov, G. V. Soviet Astr. 19, 115–116 (1975).
5. Paczynski, B. Acta astr. 41, 257–267 (1991).