@misc{indiciaea8c935782d2a,
  title = {Quality of surface waters of the United States, 1966, Parts 5 and 6, Hudson Bay and upper Mississippi River basins, and Missouri River basin},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1971},
  doi = {10.3133/wsp1993},
  url = {https://pubs.usgs.gov/publication/wsp1993},
  note = {Source identifier: wsp1993}
}