@misc{indiciaea62e176c6192,
  title = {Historical trends of U.S. mineral statistics for gold, silver, and the rare earth elements},
  author = {D.Z. Piper and E.B. Amey and H.E. Hilliard and J.B. Hedrick and N. Galtseva and W. J. Nokleberg},
  year = {1999},
  doi = {10.3133/ofr9939},
  url = {https://pubs.usgs.gov/publication/ofr9939},
  note = {Source identifier: ofr9939}
}