@misc{indiciaea45a9bdd023b,
  title = {Aeromagnetic map of Philadelphia and vicinity, Pennsylvania},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1974},
  doi = {10.3133/ofr74370},
  url = {https://pubs.usgs.gov/publication/ofr74370},
  note = {Source identifier: ofr74370}
}