@misc{indiciae79bdb9a9760e,
  title = {Preliminary geologic map of the northwest part of the Flint Hill quadrangle, Fall River County, South Dakota},
  author = {Henry Bell and E.V. Post},
  year = {1957},
  doi = {10.3133/mf61},
  url = {https://pubs.usgs.gov/publication/mf61},
  note = {Source identifier: mf61}
}