@misc{indiciae4642b980d9a2,
  title = {A stratigraphic coding system for data entry into the National Coal Resources Data System},
  author = {B.S. Pierce and B.R. Schachte and M.F. Johnson},
  year = {1987},
  doi = {10.3133/ofr87448},
  url = {https://pubs.usgs.gov/publication/ofr87448},
  note = {Source identifier: ofr87448}
}