@misc{indiciae35ca11b8afeb,
  title = {Configuration of the bedrock surface of the District of Columbia and vicinity},
  author = {N. H. Darton},
  year = {1950},
  doi = {10.3133/pp217},
  url = {https://pubs.usgs.gov/publication/pp217},
  note = {Source identifier: pp217}
}