@misc{indiciae04b494371243,
  title = {Standards for the classification of public coal lands},
  author = {N. Wood Bass and Henry L. Smith and George Henry Horn},
  year = {1970},
  doi = {10.3133/cir633},
  url = {https://pubs.usgs.gov/publication/cir633},
  note = {Source identifier: cir633}
}