@misc{indiciaef774866acf75,
  title = {Preliminary bedrock surface contour map of Montgomery County, Maryland},
  author = {A.J. Froelich},
  year = {1974},
  doi = {10.3133/ofr741036},
  url = {https://pubs.usgs.gov/publication/ofr741036},
  note = {Source identifier: ofr741036}
}