@misc{indiciaecdc68066ced9,
  title = {Defining surfaces for skewed, highly variable data},
  author = {D.R. Helsel and S.J. Ryker},
  year = {2002},
  doi = {10.1002/env.531},
  url = {https://pubs.usgs.gov/publication/70024419},
  note = {Source identifier: 70024419}
}