@misc{indiciaec4a1befe5007,
  title = {Mineral resources of the United States, 1921: Part II - Nonmetals},
  author = {Gerald Francis Loughlin and Frank James Katz},
  year = {1924},
  doi = {10.3133/70175846},
  url = {https://pubs.usgs.gov/publication/70175846},
  note = {Source identifier: 70175846}
}