@misc{indiciae2c213ee6ba56,
  title = {Relations among pH, sulfate, and metals concentrations in anthracite and bituminous coal-mine discharges, Pennsylvania},
  author = {III Cravotta},
  year = {2006},
  url = {https://pubs.usgs.gov/publication/70189257},
  note = {Source identifier: 70189257}
}