@misc{indiciaec052497bda30,
  title = {Production data for the upper Mississippi Valley lead-zinc district},
  author = {A.V. Heyl and A.F. Agnew and E.J. Lyons and C. H. Behre},
  year = {1959},
  doi = {10.3133/ofr5953},
  url = {https://pubs.usgs.gov/publication/ofr5953},
  note = {Source identifier: ofr5953}
}