@misc{indiciae4fe837aecc02,
  title = {Guide to selected large-scale geologic maps of southwestern Pennsylvania (west of 78 degrees 45' meridian and south 41 degrees 15' parallel)},
  author = {R. P. Briggs},
  year = {1973},
  doi = {10.3133/ofr7332},
  url = {https://pubs.usgs.gov/publication/ofr7332},
  note = {Source identifier: ofr7332}
}