@misc{indiciae7baae41ab883,
  title = {National water-quality assessment program; the Potomac River basin},
  author = {J. M. Gerhart},
  year = {1991},
  doi = {10.3133/ofr91157},
  url = {https://pubs.usgs.gov/publication/ofr91157},
  note = {Source identifier: ofr91157}
}