@misc{indiciae63c19ca6f2a7,
  title = {Geologic map of the Empire quadrangle, Grand, Gilpin, and Clear Creek Counties, Colorado},
  author = {William A. Braddock},
  year = {1967},
  doi = {10.3133/ofr6727},
  url = {https://pubs.usgs.gov/publication/ofr6727},
  note = {Source identifier: ofr6727}
}