@misc{indiciae533dbd715b3a,
  title = {Mining geology of the Pond Creek seam, Pikeville Formation, Middle Pennsylvanian, in part of the Eastern Kentucky Coal Field, USA},
  author = {S.F. Greb and J.T. Popp},
  year = {1999},
  doi = {10.1016/s0166-5162(99)00010-5},
  url = {https://pubs.usgs.gov/publication/70021933},
  note = {Source identifier: 70021933}
}