@misc{indiciae240b267a8d91,
  title = {Geologic map of the Olney quadrangle, Caldwell and Hopkins Counties, Kentucky},
  author = {Robert Denny Trace and Thomas M. Kehn},
  year = {1968},
  doi = {10.3133/gq742},
  url = {https://pubs.usgs.gov/publication/gq742},
  note = {Source identifier: gq742}
}