@misc{indiciaea2b1efc2593d,
  title = {Economic geology of the Georgetown quadrangle (together with the Empire district), Colorado},
  author = {Josiah E. Spurr and George H. Garrey and Sydney H. Ball},
  year = {1908},
  doi = {10.3133/pp63},
  url = {https://pubs.usgs.gov/publication/pp63},
  note = {Source identifier: pp63}
}