@misc{indiciae8f9c233efe32,
  title = {IGRFGRID : a program for creation of a total magnetic field (International Geomagnetic Reference Field) grid representing the earth's main magnetic field, Part A - Documentation},
  author = {Ronald E. Sweeney},
  year = {1990},
  doi = {10.3133/ofr9045a},
  url = {https://pubs.usgs.gov/publication/ofr9045A},
  note = {Source identifier: ofr9045A}
}