@misc{indiciaeaefe0134704b,
  title = {Precambrian geology of the Needle mountains, southwestern Colorado},
  author = {Fred Barker},
  year = {1969},
  doi = {10.3133/pp644a},
  url = {https://pubs.usgs.gov/publication/pp644A},
  note = {Source identifier: pp644A}
}