@misc{indiciaea47b6efa6b5e,
  title = {Bentonite deposits of the northern Black Hills district, Montana, Wyoming, and South Dakota},
  author = {M. M. Knechtel and S. H. Patterson},
  year = {1955},
  doi = {10.3133/mf36},
  url = {https://pubs.usgs.gov/publication/mf36},
  note = {Source identifier: mf36}
}