@misc{indiciae3db05ef9e7c4,
  title = {Geology of the northern Black Hills bentonite mining district},
  author = {Sam H. Patterson},
  year = {1955},
  doi = {10.3133/ofr55131},
  url = {https://pubs.usgs.gov/publication/ofr55131},
  note = {Source identifier: ofr55131}
}