@misc{indiciaeaf139deef8fa,
  title = {The geologic time classification of the United States Geological Survey compared with other classifications, accompanied by the original definitions of era, period and epoch terms},
  author = {Mary Grace Wilmarth},
  year = {1925},
  doi = {10.3133/b769},
  url = {https://pubs.usgs.gov/publication/b769},
  note = {Source identifier: b769}
}