@misc{indiciaef9ec8cc73242,
  title = {Coal petrographic laboratory procedures and safety manual II},
  author = {J. Pontolillo and R.W. Stanton},
  year = {1994},
  doi = {10.3133/ofr94631},
  url = {https://pubs.usgs.gov/publication/ofr94631},
  note = {Source identifier: ofr94631}
}