@misc{indiciae1cf621b7c49e,
  title = {Coal-bearing Upper Pennsylvanian and Lower Permian rocks, Washington area, Pennsylvania},
  author = {Henry L. Berryhill and Stanley P. Schweinfurth and Bion H. Kent},
  year = {1971},
  doi = {10.3133/pp621},
  url = {https://pubs.usgs.gov/publication/pp621},
  note = {Source identifier: pp621}
}