@misc{indiciae06419c091b13,
  title = {Hydrologic Unit Map -- 1974, State of Pennsylvania},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1974},
  doi = {10.3133/hu39},
  url = {https://pubs.usgs.gov/publication/hu39},
  note = {Source identifier: hu39}
}