@misc{indiciaef835525c16f2,
  title = {Digital computer map showing conformation of the bedrock surface, Montgomery County, Maryland},
  author = {J. Nicholas Van Driel},
  year = {1975},
  doi = {10.3133/ofr75418},
  url = {https://pubs.usgs.gov/publication/ofr75418},
  note = {Source identifier: ofr75418}
}