S. Komossa, V. Burwitz, G. Hasinger, P.Predehl, J. S. Kaastra, Y. Ikebe (2003). “Discovery of a Binary Active Galactic Nucleus in the Ultraluminous Infrared Galaxy NGC 6240 Using Chandra”. Astrophysical Journal582 (1): L15-L19. arXiv:astro-ph/0212099. Bibcode: 2003ApJ...582L..15K. doi:10.1086/346145.
S. Komossa, V. Burwitz, G. Hasinger, P.Predehl, J. S. Kaastra, Y. Ikebe (2003). “Discovery of a Binary Active Galactic Nucleus in the Ultraluminous Infrared Galaxy NGC 6240 Using Chandra”. Astrophysical Journal582 (1): L15-L19. arXiv:astro-ph/0212099. Bibcode: 2003ApJ...582L..15K. doi:10.1086/346145.
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J. W. Fried, H. Schulz (1983). “NGC 6240 - A unique interacting galaxy”. Astronomy and Astrophysics118: 166-170. Bibcode: 1983A&A...118..166F.
S. Komossa, V. Burwitz, G. Hasinger, P.Predehl, J. S. Kaastra, Y. Ikebe (2003). “Discovery of a Binary Active Galactic Nucleus in the Ultraluminous Infrared Galaxy NGC 6240 Using Chandra”. Astrophysical Journal582 (1): L15-L19. arXiv:astro-ph/0212099. Bibcode: 2003ApJ...582L..15K. doi:10.1086/346145.