@misc{indiciae3c3b2f1ba1a7,
  title = {Optimal parking orbits for manned Mars missions},
  author = {Cupples, Michael L. and Nordwall, Jill A.},
  year = {1993},
  url = {https://ntrs.nasa.gov/citations/19950049788},
  note = {Source identifier: 19950049788}
}