@misc{indiciae945ac0f9c384,
  title = {Thickness and lithology of Upper Ordovician and Lower and Middle Silurian rocks in the Michigan basin},
  author = {G. V. Cohee},
  year = {1948},
  doi = {10.3133/oc33},
  url = {https://pubs.usgs.gov/publication/oc33},
  note = {Source identifier: oc33}
}