@misc{indiciaea0781aedcf70,
  title = {The magnetic field of the Earth, 1990: Horizontal intensity chart},
  author = {N.W. Peddie},
  year = {1993},
  doi = {10.3133/gp1004h},
  url = {https://pubs.usgs.gov/publication/gp1004H},
  note = {Source identifier: gp1004H}
}