@misc{indiciaeff810b778303,
  title = {Characterization of humic acid fractions by C-13 nuclear magnetic resonance spectroscopy},
  author = {Robert L. Wershaw and Kevin A. Thorn and D.J. Pinckney},
  year = {1988},
  doi = {10.1080/09593338809384538},
  url = {https://pubs.usgs.gov/publication/70014847},
  note = {Source identifier: 70014847}
}