@misc{indiciaeb2e954f323d1,
  title = {Geologic map of the Penn Mine, Calaveras County, California},
  author = {J.A. Peterson},
  year = {1985},
  doi = {10.3133/mf1797},
  url = {https://pubs.usgs.gov/publication/mf1797},
  note = {Source identifier: mf1797}
}