@misc{indiciae554499f5d5f5,
  title = {Simple Bouguer gravity map of the northern part of the Black Hills, South Dakota},
  author = {Robert M. Hazlewood},
  year = {1964},
  doi = {10.3133/ofr6475},
  url = {https://pubs.usgs.gov/publication/ofr6475},
  note = {Source identifier: ofr6475}
}