@misc{indiciae0027e9dd6daa,
  title = {Preliminary geologic map of the Silverton Quadrangle, Colorado},
  author = {Robert G. Luedke and Wilbur S. Burbank},
  year = {1975},
  doi = {10.3133/ofr75433},
  url = {https://pubs.usgs.gov/publication/ofr75433},
  note = {Source identifier: ofr75433}
}