@misc{indiciaeafc33d69a82a,
  title = {Geologic map of anthracite-bearing rocks in the Pottsville Quadrangle, Schuylkill County, Pennsylvania},
  author = {G.H. Wood},
  year = {1972},
  doi = {10.3133/i681},
  url = {https://pubs.usgs.gov/publication/i681},
  note = {Source identifier: i681}
}