@misc{indiciaee66e81ffb2d4,
  title = {Maps showing bedrock outcrops in the Concord, Lexington, Boston North, Reading, Salem, and South Groveland quadrangles, Massachusetts},
  author = {Kenneth Granville Bell},
  year = {1976},
  doi = {10.3133/ofr76697},
  url = {https://pubs.usgs.gov/publication/ofr76697},
  note = {Source identifier: ofr76697}
}