@misc{indiciae8addab689aa1,
  title = {Work plan for regional reconnaissance for selected herbicides and nitrate in ground water of the mid-continent United States, 1991},
  author = {D.W. Kolpin and M. R. Burkart},
  year = {1991},
  doi = {10.3133/ofr9159},
  url = {https://pubs.usgs.gov/publication/ofr9159},
  note = {Source identifier: ofr9159}
}