1. Aharonian, F.A., 1999, AN, 320, 222.
2. Aharonian, F.A. & Atoyan, A.M., 1991, J. Phys. G: Nucl. Part. Phys., 17, 1769.
3. Aharonian, F.A., et al. (HEGRA Collaboration), 1999a, A&A, 342, 69.
4. Aharonian, F.A., et al. (HEGRA Collaboration), 1999b, A&A, 349, 11.
5. Aharonian, F.A., et al. (HEGRA Collaboration), 1999c, A&A, 350, 757.