@misc{indiciaeef2a561cd636,
  title = {Geologic map of the Olmstead quadrangle, Todd and Logan Counties, Kentucky},
  author = {George E. Ulrich},
  year = {1966},
  doi = {10.3133/gq553},
  url = {https://pubs.usgs.gov/publication/gq553},
  note = {Source identifier: gq553}
}