@misc{indiciae60a3f371b5e9,
  title = {Coal as a recorder of incipient rock metamorphism},
  author = {Marius Robinson Campbell},
  year = {1930},
  doi = {10.2113/gsecongeo.25.7.675},
  url = {https://pubs.usgs.gov/publication/70217853},
  note = {Source identifier: 70217853}
}