@misc{indiciaee4c2c75ac4fc,
  title = {Geologic map of the Calhoun quadrangle, western Kentucky},
  author = {William D. Johnson and Avery E. Smith},
  year = {1975},
  doi = {10.3133/gq1239},
  url = {https://pubs.usgs.gov/publication/gq1239},
  note = {Source identifier: gq1239}
}