@misc{indiciae8d3d39c8ed58,
  title = {Comments on the "three-step" method for quantification of undiscovered mineral resources},
  author = {M.W. Bultman and E. R. Force and M. E. Gettings and F. S. Fisher},
  year = {1993},
  doi = {10.3133/ofr9323},
  url = {https://pubs.usgs.gov/publication/ofr9323},
  note = {Source identifier: ofr9323}
}