@misc{indiciae7182ec483a7f,
  title = {Surface materials map of Montgomery County, Maryland},
  author = {A.J. Froelich},
  year = {1974},
  doi = {10.3133/ofr74154},
  url = {https://pubs.usgs.gov/publication/ofr74154},
  note = {Source identifier: ofr74154}
}