@misc{indiciae45648300afc0,
  title = {Recommended procedures and methodology of coal description},
  author = {E.C. Chao and J.A. Minkin and C.L. Thompson},
  year = {1983},
  doi = {10.3133/cir894},
  url = {https://pubs.usgs.gov/publication/cir894},
  note = {Source identifier: cir894}
}