@misc{indiciae2c7a564e0ba6,
  title = {The geology of the Wissahickon formation in Delaware},
  author = {R.F. Ward},
  year = {1956},
  doi = {10.3133/ofr56128},
  url = {https://pubs.usgs.gov/publication/ofr56128},
  note = {Source identifier: ofr56128}
}