@misc{indiciae56a42743a778,
  title = {Geologic map of the Heidelberg quadrangle, east-central Kentucky},
  author = {Douglas F. B. Black},
  year = {1977},
  doi = {10.3133/gq1340},
  url = {https://pubs.usgs.gov/publication/gq1340},
  note = {Source identifier: gq1340}
}