@misc{indiciae5989be32c931,
  title = {The magnetic field of the earth-1985: Total intensity chart},
  author = {N.W. Peddie and A.K. Zunde},
  year = {1988},
  doi = {10.3133/gp987f},
  url = {https://pubs.usgs.gov/publication/gp987F},
  note = {Source identifier: gp987F}
}