@misc{indiciaea891121887f4,
  title = {Geologic map of the Clay City quadrangle, Powell and Estill Counties, Kentucky},
  author = {George Clarke Simmons},
  year = {1967},
  doi = {10.3133/gq663},
  url = {https://pubs.usgs.gov/publication/gq663},
  note = {Source identifier: gq663}
}