@misc{indiciaea58a8acf7a48,
  title = {Geology of the Empire quadrangle, Grand, Gilpin, and Clear Creek Counties, Colorado},
  author = {William A. Braddock},
  year = {1969},
  doi = {10.3133/pp616},
  url = {https://pubs.usgs.gov/publication/pp616},
  note = {Source identifier: pp616}
}