@misc{indiciae83d214bf0adb,
  title = {Geologic map of the Montrose 30' x 60' Quadrangle, southwestern Colorado},
  author = {T. A. Steven and W. J. Hail},
  year = {1989},
  doi = {10.3133/i1939},
  url = {https://pubs.usgs.gov/publication/i1939},
  note = {Source identifier: i1939}
}