@misc{indiciaeac54dfeaac0a,
  title = {Magnetic vertical intensity in the United States; epoch 1975.0},
  author = {W. J. Jones and E.B. Fabiano},
  year = {1976},
  doi = {10.3133/i914},
  url = {https://pubs.usgs.gov/publication/i914},
  note = {Source identifier: i914}
}