@misc{indiciaef313d276e88e,
  title = {Geochemical landscapes of the conterminous United States — New map presentations for 22 elements},
  author = {N. Gustavsson and B. Bolviken and D. B. Smith and R. C. Severson},
  year = {2001},
  doi = {10.3133/pp1648},
  url = {https://pubs.usgs.gov/publication/pp1648},
  note = {Source identifier: pp1648}
}