@misc{indiciae156c737ca6a2,
  title = {An attempt to obtain a detailed declination chart from the United States magnetic anomaly map},
  author = {L.R. Alldredge},
  year = {1989},
  doi = {10.5636/jgg.41.549},
  url = {https://pubs.usgs.gov/publication/70015493},
  note = {Source identifier: 70015493}
}