@misc{indiciae13ab671a11ac,
  title = {The 1995 revision of the joint US/UK geomagnetic field models - I. Secular variation},
  author = {S. Macmillan and D.R. Barraclough and J.M. Quinn and R.J. Coleman},
  year = {1997},
  url = {https://pubs.usgs.gov/publication/70019514},
  note = {Source identifier: 70019514}
}