@misc{indiciaed73a4f7aa3d1,
  title = {Four reference soil and rock samples for measuring element availability in the Western Energy Regions},
  author = {J.G. Crock and R. C. Severson},
  year = {1980},
  doi = {10.3133/cir841},
  url = {https://pubs.usgs.gov/publication/cir841},
  note = {Source identifier: cir841}
}