@misc{indiciae2a9d3a50ea59,
  title = {The Permian phosphorite deposits of western United States},
  author = {V.E. McKelvey and Roger Warren Swanson and Richard Porter Sheldon},
  year = {1952},
  doi = {10.3133/ofr53166},
  url = {https://pubs.usgs.gov/publication/ofr53166},
  note = {Source identifier: ofr53166}
}