@misc{indiciae19d09ccac133,
  title = {Stratigraphic framework and distribution of lignite in the Claiborne Group, Calhoun County, Arkansas},
  author = {B.S. Hackman},
  year = {1984},
  doi = {10.3133/i1490},
  url = {https://pubs.usgs.gov/publication/i1490},
  note = {Source identifier: i1490}
}