@misc{indiciaeeb0337416b3b,
  title = {Contour map of the base of Pennsylvanian strata in eastern Kentucky},
  author = {T. Dennis Coskren},
  year = {1978},
  doi = {10.3133/ofr78893},
  url = {https://pubs.usgs.gov/publication/ofr78893},
  note = {Source identifier: ofr78893}
}