@misc{indiciae3e9f91ee5621,
  title = {Aeromagnetic map of the Salem quadrangle, Essex County, Massachusetts},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1970},
  doi = {10.3133/gp722},
  url = {https://pubs.usgs.gov/publication/gp722},
  note = {Source identifier: gp722}
}