@misc{indiciae224a9f843196,
  title = {Geologic map of the Grayson quadrangle, Carter County, Kentucky},
  author = {Charles L. Whittington and John C. Ferm},
  year = {1967},
  doi = {10.3133/gq640},
  url = {https://pubs.usgs.gov/publication/gq640},
  note = {Source identifier: gq640}
}