@misc{indiciae0c5bbcf88fc2,
  title = {Geologic structure of the Punxsutawney, Curwensville, Houtzdale, Barnesboro, and Patton quadrangles, central Pennsylvania},
  author = {G. H. Ashley and M. R. Campbell},
  year = {1913},
  doi = {10.3133/b531d},
  url = {https://pubs.usgs.gov/publication/b531D},
  note = {Source identifier: b531D}
}