@misc{indiciae21b1cc673564,
  title = {Factors related to the water-yielding potential of rocks in the Piedmont and Valley and Ridge provinces of Pennsylvania},
  author = {D.S. Knopman},
  year = {1990},
  doi = {10.3133/wri904174},
  url = {https://pubs.usgs.gov/publication/wri904174},
  note = {Source identifier: wri904174}
}