@misc{indiciae3a0cf9424151,
  title = {Active Galactic Nuclei, Quasars, BL Lac Objects and X-Ray Background},
  author = {Mushotzky, Richard and Elvis, Martin},
  year = {2005},
  url = {https://ntrs.nasa.gov/citations/20050041631},
  note = {Source identifier: 20050041631}
}