@misc{indiciae3201521e7454,
  title = {Nitrate in the Mississippi River and its tributaries, 1980 to 2008: Are we making progress?},
  author = {Lori A. Sprague and Robert M. Hirsch and Brent T. Aulenbach},
  year = {2011},
  doi = {10.1021/es201221s},
  url = {https://pubs.usgs.gov/publication/70006337},
  note = {Source identifier: 70006337}
}