@misc{indiciaec71256c6398c,
  title = {Preliminary report on the geology and mineralogy of clays on the Pine Ridge Indian Reservation, South Dakota, with a chapter on usability tests},
  author = {Leonard Gene Schultz and Howard P. Hamlin},
  year = {1961},
  doi = {10.3133/ofr61153},
  url = {https://pubs.usgs.gov/publication/ofr61153},
  note = {Source identifier: ofr61153}
}