@misc{indiciaecd7899363707,
  title = {Geologic map of Loudoun County, Virginia},
  author = {W. C. Burton and A.J. Froelich and J.S. Schindler and C.S. Southworth},
  year = {1993},
  doi = {10.3133/ofr92716},
  url = {https://pubs.usgs.gov/publication/ofr92716},
  note = {Source identifier: ofr92716}
}