@misc{indiciaef54f71a97850,
  title = {Grade and tonnage model of Porphyry Cu deposits in British Columbia, Canada, and Alaska, U.S.A.},
  author = {W. David Menzie and Donald A. Singer},
  year = {1993},
  doi = {10.3133/ofr93275},
  url = {https://pubs.usgs.gov/publication/ofr93275},
  note = {Source identifier: ofr93275}
}