@misc{indiciae86c20817f0fa,
  title = {Geologic map of the Black Canyon of the Gunnison River and vicinity, western Colorado},
  author = {W. R. Hansen},
  year = {1971},
  doi = {10.3133/i584},
  url = {https://pubs.usgs.gov/publication/i584},
  note = {Source identifier: i584}
}