@misc{indiciaead46fd8eb55d,
  title = {The Upper Pennsylvanian Pittsburgh coal bed: Resources and mine models},
  author = {W.D. Watson and L.F. Ruppert and S.J. Tewalt and L. J. Bragg},
  year = {2001},
  doi = {10.1023/a:1011529430807},
  url = {https://pubs.usgs.gov/publication/70022814},
  note = {Source identifier: 70022814}
}