@misc{indiciae9480fdb4aa2c,
  title = {X-ray image of the Cygnus Loop},
  author = {Rappaport, S. and Petre, R. and Kayat, M. A. and Evans, K. D. and Smith, G. C. and Levine, A.},
  year = {1979},
  url = {https://ntrs.nasa.gov/citations/19790036167},
  note = {Source identifier: 19790036167}
}