@misc{indiciae054c337bc2c1,
  title = {Hydrogeologic, water-quality, and land-use data for the reconnaissance of herbicides and nitrate in near-surface aquifers of the Midcontinental United States, 1991},
  author = {D.W. Kolpin and M. R. Burkart and E.M. Thurman},
  year = {1993},
  doi = {10.3133/ofr93114},
  url = {https://pubs.usgs.gov/publication/ofr93114},
  note = {Source identifier: ofr93114}
}