@misc{indiciaebdab622ba727,
  title = {Geology and phosphate deposits of the Permian rocks in central western Montana},
  author = {R. W. Swanson},
  year = {1973},
  doi = {10.3133/pp313f},
  url = {https://pubs.usgs.gov/publication/pp313F},
  note = {Source identifier: pp313F}
}