@misc{indiciaea640c5556837,
  title = {Lead isotopes from the Upper Mississippi Valley district: A regional perspective},
  author = {Timothy M. Millen and Robert E. Zartman and Allen Van Heyl},
  year = {1995},
  doi = {10.3133/b2094b},
  url = {https://pubs.usgs.gov/publication/b2094B},
  note = {Source identifier: b2094B}
}