@misc{indiciae7e78171c2601,
  title = {Trends in the nutrient enrichment of U.S. rivers during the late 20th century and their relation to changes in probable stream trophic conditions},
  author = {R. B. Alexander and R. A. Smith},
  year = {2006},
  url = {https://pubs.usgs.gov/publication/70031059},
  note = {Source identifier: 70031059}
}