@misc{indiciae83aa8ebda049,
  title = {Plant and miscellaneous microfossils of the Pierre Shale},
  author = {Estella B. Leopold and Bernadine D. Tschudy},
  year = {1965},
  doi = {10.3133/ofr6597},
  url = {https://pubs.usgs.gov/publication/ofr6597},
  note = {Source identifier: ofr6597}
}