@misc{indiciaec41b95272278,
  title = {Nitrate in groundwater of the midwestern United States: A regional investigation on relations to land use and soil properties},
  author = {D. Kolpin and M. Burkart and D. Goolsby},
  year = {1999},
  url = {https://pubs.usgs.gov/publication/70020921},
  note = {Source identifier: 70020921}
}