@misc{indiciae7d03f76bb377,
  title = {An introduction to quiet daily geomagnetic fields},
  author = {W.H. Campbell},
  year = {1989},
  doi = {10.1007/bf00876831},
  url = {https://pubs.usgs.gov/publication/70015664},
  note = {Source identifier: 70015664}
}