@misc{indiciaefaea773b42ad,
  title = {Historical trends in U.S. mineral statistics for selected non-ferrous metals},
  author = {David Z. Piper and Warren J. Nokleberg},
  year = {2002},
  doi = {10.3133/ofr0229},
  url = {https://pubs.usgs.gov/publication/ofr0229},
  note = {Source identifier: ofr0229}
}