@misc{indiciae21a41ce8cb30,
  title = {National geochemical data base; PLUTO geochemical data base for the United States},
  author = {Philip A. Baedecker and Jeffrey N. Grossman and Kim P. Buttleman},
  year = {1998},
  doi = {10.3133/ds47},
  url = {https://pubs.usgs.gov/publication/ds47},
  note = {Source identifier: ds47}
}