@misc{indiciae3dda11b7d4fb,
  title = {Geology of the Fort Smith district, Arkansas},
  author = {T. A. Hendricks and Bryan Parks},
  year = {1950},
  doi = {10.3133/pp221e},
  url = {https://pubs.usgs.gov/publication/pp221E},
  note = {Source identifier: pp221E}
}