@misc{indiciae03135cca74b6,
  title = {Principles of the mineral resource classification system of the U.S. Bureau of Mines and U.S. Geological Survey},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1976},
  doi = {10.3133/b1450a},
  url = {https://pubs.usgs.gov/publication/b1450A},
  note = {Source identifier: b1450A}
}