@misc{indiciae1af791b6e5c2,
  title = {Ordovician and Silurian coral faunas of western United States},
  author = {Helen Duncan},
  year = {1956},
  doi = {10.3133/b1021f},
  url = {https://pubs.usgs.gov/publication/b1021F},
  note = {Source identifier: b1021F}
}