@misc{indiciaea0e9eec25912,
  title = {Aeromagnetic map of the Downingtown quadrangle, Chester County, Pennsylvania},
  author = {Randolph Wilson Bromery and G. L. Zandle},
  year = {1960},
  doi = {10.3133/gp224},
  url = {https://pubs.usgs.gov/publication/gp224},
  note = {Source identifier: gp224}
}