@misc{indiciae685d29da8ee3,
  title = {Geologic map of Butler County, Pennsylvania},
  author = {E. D. Patterson and J. A. Van Lieu},
  year = {1962},
  doi = {10.3133/ofr6298},
  url = {https://pubs.usgs.gov/publication/ofr6298},
  note = {Source identifier: ofr6298}
}