@misc{indiciae178bce6330f1,
  title = {Interstellar Exploration: Propulsion Options for Precursors and Beyond},
  author = {Leifer, S. and Johnson, L.},
  year = {1999},
  url = {https://ntrs.nasa.gov/citations/20060040897},
  note = {Source identifier: 20060040897}
}