@misc{indiciaee40b47353c6d,
  title = {The magnetic field of the earth— 1985: Horizontal intensity chart},
  author = {N.W. Peddie and A.K. Zunde},
  year = {1988},
  doi = {10.3133/gp987h},
  url = {https://pubs.usgs.gov/publication/gp987H},
  note = {Source identifier: gp987H}
}