@misc{indiciaebd17d74eb233,
  title = {Coal resources of Butler County, Pennsylvania},
  author = {E. D. Patterson and J. A. Van Lieu},
  year = {1971},
  doi = {10.3133/b1143c},
  url = {https://pubs.usgs.gov/publication/b1143C},
  note = {Source identifier: b1143C}
}