@misc{indiciaea2b32d609f33,
  title = {A summary of phosphate-rock resources of the United States-an analysis of past estimates},
  author = {James Bachelder Cathcart and Richard Porter Sheldon and Robert A. Gulbrandsen},
  year = {1981},
  doi = {10.3133/ofr81789},
  url = {https://pubs.usgs.gov/publication/ofr81789},
  note = {Source identifier: ofr81789}
}