@misc{indiciae6a15866a034d,
  title = {Nutrients in the Nation's waters; identifying problems and progress},
  author = {Elisabeth A. Graffy and Dennis R. Helsel and David K. Mueller},
  year = {1996},
  doi = {10.3133/fs21896},
  url = {https://pubs.usgs.gov/publication/fs21896},
  note = {Source identifier: fs21896}
}