@misc{indiciae2670b26ff97d,
  title = {Geologic map of the Loudoun County, Virginia, part of the Harpers Ferry Quadrangle},
  author = {C.S. Southworth},
  year = {1991},
  doi = {10.3133/mf2173},
  url = {https://pubs.usgs.gov/publication/mf2173},
  note = {Source identifier: mf2173}
}