@misc{indiciae0e0ec635531d,
  title = {Natural background concentrations of nutrients in streams and rivers of the conterminous United States},
  author = {R. A. Smith and R. B. Alexander and G. E. Schwarz},
  year = {2003},
  doi = {10.1021/es020663b},
  url = {https://pubs.usgs.gov/publication/70025473},
  note = {Source identifier: 70025473}
}