@misc{indiciae7b0215443a54,
  title = {Mineral resources of the United States, 1920: Part II - Nonmetals},
  author = {Gerald Francis Loughlin and Ralph Walter Stone},
  year = {1923},
  doi = {10.3133/70175844},
  url = {https://pubs.usgs.gov/publication/70175844},
  note = {Source identifier: 70175844}
}