@misc{indiciae678138f7845c,
  title = {Selenium, fluorine, and arsenic in surficial materials of the conterminous United States},
  author = {Hansford T. Shacklette and Josephine G. Boerngen and John R. Keith},
  year = {1974},
  doi = {10.3133/cir692},
  url = {https://pubs.usgs.gov/publication/cir692},
  note = {Source identifier: cir692}
}