@misc{indiciae00b56bb35602,
  title = {Mercury in the environment; surficial materials of the conterminous United States},
  author = {Hansford T. Shacklette and Josephine G. Boerngen and Robert L. Turner},
  year = {1971},
  doi = {10.3133/cir644},
  url = {https://pubs.usgs.gov/publication/cir644},
  note = {Source identifier: cir644}
}