@misc{indiciae6a3f895c3507,
  title = {Preliminary composite magnetic anomaly map of part of the Northwestern United States},
  author = {Isidore Zietz},
  year = {1981},
  doi = {10.3133/ofr81835},
  url = {https://pubs.usgs.gov/publication/ofr81835},
  note = {Source identifier: ofr81835}
}