@misc{indiciaea97eb003e871,
  title = {Elemental composition of surficial materials in the conterminous United States},
  author = {H.T. Shacklette and J. C. Hamilton and J.G. Boerngen and J.M. Bowles},
  year = {1971},
  doi = {10.3133/pp574d},
  url = {https://pubs.usgs.gov/publication/pp574D},
  note = {Source identifier: pp574D}
}