@misc{indiciae20b0d5b4958f,
  title = {Fluorospar Investigations: Preliminary Report on the Geology of the Columbia Mine Area, Crittenden County, Kentucky},
  author = {G. C. Hardin},
  year = {1944},
  doi = {10.3133/ofr4411},
  url = {https://pubs.usgs.gov/publication/ofr4411},
  note = {Source identifier: ofr4411}
}