@misc{indiciaeaf5a8978ff96,
  title = {Field description and sampling of coal beds},
  author = {James Morton Schopf},
  year = {1960},
  doi = {10.3133/b1111b},
  url = {https://pubs.usgs.gov/publication/b1111B},
  note = {Source identifier: b1111B}
}