@misc{indiciaec2d762351209,
  title = {Map of rock types in bedrock of Allegheny County, Pennsylvania},
  author = {W. R. Kohl and R. P. Briggs},
  year = {1975},
  doi = {10.3133/mf685a},
  url = {https://pubs.usgs.gov/publication/mf685A},
  note = {Source identifier: mf685A}
}