@misc{indiciae6333935deb3d,
  title = {Economic analysis of maximum economic recovery of Federal coal},
  author = {William Watson and Richard L. Bernknopf},
  year = {1979},
  doi = {10.3133/ofr791142},
  url = {https://pubs.usgs.gov/publication/ofr791142},
  note = {Source identifier: ofr791142}
}