@misc{indiciae18d6956c9879,
  title = {Simultaneous multifrequency observations of Markarian 421},
  author = {Brodie, Jean and Bowyer, Stuart and Tennant, Allyn},
  year = {1987},
  url = {https://ntrs.nasa.gov/citations/19870059313},
  note = {Source identifier: 19870059313}
}