@misc{indiciaef03db571c607,
  title = {Principles of a resource/reserve classification for minerals},
  author = {U.S. Bureau of Mines and U.S. Geological Survey},
  year = {1980},
  doi = {10.3133/cir831},
  url = {https://pubs.usgs.gov/publication/cir831},
  note = {Source identifier: cir831}
}