@misc{indiciae154cf12ec1b3,
  title = {Bouguer gravity, aeromagnetic, and generalized geologic maps of part of the Black Hills of South Dakota and Wyoming},
  author = {M. D. Kleinkopf and J. A. Redden},
  year = {1975},
  doi = {10.3133/gp903},
  url = {https://pubs.usgs.gov/publication/gp903},
  note = {Source identifier: gp903}
}