@misc{indiciae2eed26740a60,
  title = {Coal map of North America},
  author = {Gordon H. Wood and William V. Bour},
  year = {1988},
  doi = {10.3133/70211098},
  url = {https://pubs.usgs.gov/publication/70211098},
  note = {Source identifier: 70211098}
}