@misc{indiciae7ea21e39c106,
  title = {Geology and ore deposits of the South Silverton mining area, San Juan County, Colorado},
  author = {David J. Varnes},
  year = {1963},
  doi = {10.3133/pp378a},
  url = {https://pubs.usgs.gov/publication/pp378A},
  note = {Source identifier: pp378A}
}