@misc{indiciae8fcd1d2fc23f,
  title = {Discovery of phosphate rock in Saudi Arabia and recommended program of further study},
  author = {Richard Porter Sheldon},
  year = {1967},
  doi = {10.3133/ofr67199},
  url = {https://pubs.usgs.gov/publication/ofr67199},
  note = {Source identifier: ofr67199}
}