@misc{indiciaef7d6976f4429,
  title = {Map of northern half of Wisconsin showing geologic data of Precambrian area},
  author = {Carl E. Dutton and Reta E. Bradley},
  year = {1968},
  doi = {10.3133/ofr6891},
  url = {https://pubs.usgs.gov/publication/ofr6891},
  note = {Source identifier: ofr6891}
}