@misc{indiciae93552cf9e8b5,
  title = {Topographic map of the Palisades-Unkar area, Grand Canyon, Arizona},
  author = {Ivo Lucchitta},
  year = {1991},
  doi = {10.3133/ofr91636},
  url = {https://pubs.usgs.gov/publication/ofr91636},
  note = {Source identifier: ofr91636}
}