@misc{indiciae6aeaa1c95f92,
  title = {Preliminary integrated geologic map databases for the United States: Minnesota, Wisconsin, Michigan, Illinois, and Indiana},
  author = {Suzanne W. Nicholson and Connie L. Dicken and Michael P. Foose and Julie Mueller},
  year = {2004},
  doi = {10.3133/ofr20041355},
  url = {https://pubs.usgs.gov/publication/ofr20041355},
  note = {Source identifier: ofr20041355}
}