@misc{indiciae56996b501505,
  title = {Geologic map of the Ishpeming Quadrangle, Marquette County, Michigan},
  author = {G. C. Simmons},
  year = {1971},
  doi = {10.3133/ofr71259},
  url = {https://pubs.usgs.gov/publication/ofr71259},
  note = {Source identifier: ofr71259}
}