@misc{indiciaefed3ea24f8ff,
  title = {Coal fields of the conterminous United States},
  author = {John Tully},
  year = {1996},
  doi = {10.3133/ofr9692},
  url = {https://pubs.usgs.gov/publication/ofr9692},
  note = {Source identifier: ofr9692}
}