@misc{indiciae04ccd04ea6ec,
  title = {Twenty-Third Annual report of the Director of the United States Geological Survey, 1901-1902},
  author = {Charles D. Walcott},
  year = {1902},
  doi = {10.3133/ar23},
  url = {https://pubs.usgs.gov/publication/ar23},
  note = {Source identifier: ar23}
}