@misc{indiciaeff891bb95cb6,
  title = {The Fire Clay and Whitesburg coals in the Hyden quadrangle, Leslie, Clay, and Perry Counties, Kentucky},
  author = {John Edward Johnston and W. A. Heck},
  year = {1950},
  doi = {10.3133/coal5},
  url = {https://pubs.usgs.gov/publication/coal5},
  note = {Source identifier: coal5}
}