@misc{indiciaeab18149d33dd,
  title = {Preliminary correlation chart of coal beds and key beds of the Pennsylvanian rocks of eastern Kentucky},
  author = {Charles L. Rice and J. Hiram Smith},
  year = {1979},
  doi = {10.3133/ofr79867},
  url = {https://pubs.usgs.gov/publication/ofr79867},
  note = {Source identifier: ofr79867}
}