@misc{indiciae2238a0b4df7a,
  title = {Geologic map of the Providence quadrangle, western Kentucky},
  author = {Thomas M. Kehn},
  year = {1966},
  doi = {10.3133/gq491},
  url = {https://pubs.usgs.gov/publication/gq491},
  note = {Source identifier: gq491}
}