@misc{indiciaea525805be18c,
  title = {Earth orbital experiment program and requirements study. Volume 4: Space astronomy (appendices A, B, C, D) and space physics (appendices A, B, C)},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19730014054},
  note = {Source identifier: 19730014054}
}