@misc{indiciae3b2aa9dfaf00,
  title = {Zinc-lead-copper resources and general geology of the Upper Mississippi Valley district},
  author = {Allen Van Heyl and E.J. Lyons and A.F. Agnew and C. H. Behre},
  year = {1955},
  doi = {10.3133/b1015g},
  url = {https://pubs.usgs.gov/publication/b1015G},
  note = {Source identifier: b1015G}
}