@misc{indiciae7cd158d736c3,
  title = {Maps showing platinum-group-element occurrences in the conterminous United States, updated as of 1993},
  author = {J.A. Peterson},
  year = {1994},
  doi = {10.3133/mf2270},
  url = {https://pubs.usgs.gov/publication/mf2270},
  note = {Source identifier: mf2270}
}