@misc{indiciae12095bad643a,
  title = {Surficial geologic map of parts of Billerica, Wilmington, and Lexington quadrangles, Massachusetts},
  author = {Robert O. Castle},
  year = {1950},
  doi = {10.3133/ofr5031},
  url = {https://pubs.usgs.gov/publication/ofr5031},
  note = {Source identifier: ofr5031}
}