@misc{indiciaefb4abedc58a7,
  title = {Bedrock geologic map of the St. Louis 30' x 60' Quadrangle, Missouri and Illinois},
  author = {R. W. Harrison},
  year = {1997},
  doi = {10.3133/i2533},
  url = {https://pubs.usgs.gov/publication/i2533},
  note = {Source identifier: i2533}
}