@misc{indiciaef2fe9afeab75,
  title = {Geologic map of the Gracey quadrangle, Trigg and Christian Counties, Kentucky},
  author = {Willis H. Nelson and David Arthur Seeland},
  year = {1968},
  doi = {10.3133/gq753},
  url = {https://pubs.usgs.gov/publication/gq753},
  note = {Source identifier: gq753}
}