@misc{indiciae27a5cd98c2b4,
  title = {Geologic map of the Heidrick quadrangle, Knox and Laurel Counties, Kentucky},
  author = {Donald E. Trimble and J. Hiram Smith},
  year = {1978},
  doi = {10.3133/gq1501},
  url = {https://pubs.usgs.gov/publication/gq1501},
  note = {Source identifier: gq1501}
}