@misc{indiciae0c85adf11a9e,
  title = {Stratospheric Observatory for Infrared Astronomy (SOFIA) system concept},
  author = {Wiltsee, Christopher B. and Brooks, Walter F.},
  year = {1989},
  url = {https://ntrs.nasa.gov/citations/19900024211},
  note = {Source identifier: 19900024211}
}