@misc{indiciaeab8b359147ac,
  title = {Geologic map of the Hellertown Quadrangle, Northampton, Bucks, and Lehigh counties, Pennsylvania},
  author = {Avery A. Drake},
  year = {1996},
  doi = {10.3133/ofr96547},
  url = {https://pubs.usgs.gov/publication/ofr96547},
  note = {Source identifier: ofr96547}
}