@misc{indiciae8beb186cc38a,
  title = {Aeromagnetic and inferred Precambrian paleogeologic map of east-central Minnesota and part of Wisconsin},
  author = {P.K. Sims and Isidore Zietz},
  year = {1967},
  doi = {10.3133/gp563},
  url = {https://pubs.usgs.gov/publication/gp563},
  note = {Source identifier: gp563}
}