@misc{indiciae5f28a425b521,
  title = {Map showing areal extent of the Pittsburgh Coal Bed and horizon and mined areas of the Pittsburgh Coal Bed in Pennsylvania, Ohio, West Virginia, and Maryland},
  author = {Leslie F. Ruppert and S.J. Tewalt and L. J. Bragg and John Tully and J. Pierce and A. Weller and Jeanette Yarnell},
  year = {1996},
  doi = {10.3133/ofr96280},
  url = {https://pubs.usgs.gov/publication/ofr96280},
  note = {Source identifier: ofr96280}
}