@misc{indiciae62a6cd0d7743,
  title = {Aeromagnetic and tectonic analysis of the Upper Mississippi Valley zinc-lead district},
  author = {Allen Van Heyl and Elizabeth R. King},
  year = {1966},
  doi = {10.3133/b1242a},
  url = {https://pubs.usgs.gov/publication/b1242A},
  note = {Source identifier: b1242A}
}