@misc{indiciae7fb1d38ec84e,
  title = {Aeromagnetic map of the Grafton quadrangle, Worcester County, Massachusetts},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1971},
  doi = {10.3133/gp759},
  url = {https://pubs.usgs.gov/publication/gp759},
  note = {Source identifier: gp759}
}