@misc{indiciae36fe5b368ed7,
  title = {Coal fields of the United States},
  author = {James Trumbull and Farrell F. Barnes},
  year = {1960},
  doi = {10.3133/70043342},
  url = {https://pubs.usgs.gov/publication/70043342},
  note = {Source identifier: 70043342}
}