@misc{indiciae91ef3c4f5251,
  title = {Geology of the Billows quadrangle, Kentucky},
  author = {Norman L. Hatch},
  year = {1963},
  doi = {10.3133/gq228},
  url = {https://pubs.usgs.gov/publication/gq228},
  note = {Source identifier: gq228}
}