@misc{indiciae9121872a5671,
  title = {Photographs of historical mining operations in Colorado and Utah from the U.S. Geological Survey Library},
  author = {Joseph K. McGregor and C. C. Abston},
  year = {1994},
  doi = {10.3133/ds12},
  url = {https://pubs.usgs.gov/publication/ds12},
  note = {Source identifier: ds12}
}