@misc{indiciae7d9bc2d4c964,
  title = {Geology and mineral resources of the Peoria quadrangle, Illinois},
  author = {Johan August Udden},
  year = {1912},
  doi = {10.3133/b506},
  url = {https://pubs.usgs.gov/publication/b506},
  note = {Source identifier: b506}
}