@misc{indiciaec14c2c3fbf4a,
  title = {Coal resources of the United States, A progress report, November 1, 1950},
  author = {Paul Averitt and Louise R. Berryhill},
  year = {1950},
  doi = {10.3133/cir94},
  url = {https://pubs.usgs.gov/publication/cir94},
  note = {Source identifier: cir94}
}