@misc{indiciaeb7e6e4e3326a,
  title = {Geologic map of the Ballardsville quadrangle, north-central Kentucky},
  author = {Roy Clark Kepferle},
  year = {1977},
  doi = {10.3133/gq1389},
  url = {https://pubs.usgs.gov/publication/gq1389},
  note = {Source identifier: gq1389}
}