@misc{indiciae67a211595d4a,
  title = {Trend analysis of sulfate, nitrate and pH data collected at National Atmospheric Deposition Program/National Trends Network stations between 1980 and 1991},
  author = {W.G. Baier and T.A. Cohn},
  year = {1993},
  doi = {10.3133/ofr9356},
  url = {https://pubs.usgs.gov/publication/ofr9356},
  note = {Source identifier: ofr9356}
}