@misc{indiciaed2c079f24b7f,
  title = {Preliminary digital geologic map of the Penokean (early Proterozoic) continental margin in northern Michigan and Wisconsin},
  author = {W.F. Cannon and Doug Ottke},
  year = {1999},
  doi = {10.3133/ofr99547},
  url = {https://pubs.usgs.gov/publication/ofr99547},
  note = {Source identifier: ofr99547}
}