Gursky H; Kellogg EM; Leong C; Tananbaum H et al. (Apr 1971). “Detection of X-Rays from the Seyfert Galaxies NGC 1275 and NGC 4151 by the UHURU Satellite”. Ap J165 (4): L43–8. Bibcode: 1971ApJ...165L..43G. doi:10.1086/180713.
Wood KS; Meekins JF; Yentis DJ; Smathers HW et al. (December 1984). “The HEAO A-1 X-ray source catalog”. Astrophys. J. Suppl. Ser.56 (12): 507–649. Bibcode: 1984ApJS...56..507W. doi:10.1086/190992.
Gursky H; Kellogg EM; Leong C; Tananbaum H et al. (Apr 1971). “Detection of X-Rays from the Seyfert Galaxies NGC 1275 and NGC 4151 by the UHURU Satellite”. Ap J165 (4): L43–8. Bibcode: 1971ApJ...165L..43G. doi:10.1086/180713.
Wood KS; Meekins JF; Yentis DJ; Smathers HW et al. (December 1984). “The HEAO A-1 X-ray source catalog”. Astrophys. J. Suppl. Ser.56 (12): 507–649. Bibcode: 1984ApJS...56..507W. doi:10.1086/190992.