@misc{indiciae9a647c9f2c41,
  title = {Aeromagnetic map of the Pepperell quadrangle, Middlesex County, Massachusetts, and Hillsborough County, New Hampshire},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1971},
  doi = {10.3133/gp732},
  url = {https://pubs.usgs.gov/publication/gp732},
  note = {Source identifier: gp732}
}