@misc{indiciaee76d55658ec3,
  title = {Geologic reconnaissance map of the Rules Hill and Ludwig Mountain quadrangles, La Plata County, Colorado},
  author = {W. J. Hail and Harley Barnes and A.D. Zapp},
  year = {1971},
  doi = {10.3133/ofr71143},
  url = {https://pubs.usgs.gov/publication/ofr71143},
  note = {Source identifier: ofr71143}
}