@misc{indiciae03f55dce7118,
  title = {Bedrock map of Montgomery County, Maryland},
  author = {A. J. Froehlich},
  year = {1975},
  doi = {10.3133/i920d},
  url = {https://pubs.usgs.gov/publication/i920D},
  note = {Source identifier: i920D}
}