@misc{indiciae98e6298b5b9a,
  title = {Distribution of minor elements in ore and host rock, Illinois-Kentucky fluorite district and Upper Mississippi Valley zinc-lead district},
  author = {Wayne E. Hall and Allen V. Heyl},
  year = {1968},
  doi = {10.2113/gsecongeo.63.6.655},
  url = {https://pubs.usgs.gov/publication/70209022},
  note = {Source identifier: 70209022}
}