@misc{indiciae5329ccadfd62,
  title = {Stratigraphy of Middle Ordovician rocks in the zinc-lead district of Wisconsin, Illinois, and Iowa},
  author = {A.F. Agnew and A. V. Heyl and C. H. Behre and E.J. Lyons},
  year = {1956},
  doi = {10.3133/pp274k},
  url = {https://pubs.usgs.gov/publication/pp274K},
  note = {Source identifier: pp274K}
}