@misc{indiciae8486ca86ebbf,
  title = {Aeromagnetic map of Delaware, Maryland, Pennsylvania, West Virginia, and parts of New Jersey, and New York},
  author = {Isidore Zietz and F. P. Gilbert and J. R. Kirby},
  year = {1980},
  doi = {10.3133/gp927},
  url = {https://pubs.usgs.gov/publication/gp927},
  note = {Source identifier: gp927}
}