@misc{indiciae4e48bef56dcb,
  title = {A further revision of the stratigraphic nomenclature of the Wissahickon Formation in Maryland},
  author = {Michael W. Higgins and George Wescott Fisher},
  year = {1971},
  doi = {10.1130/0016-7606(1971)82[769:afrots]2.0.co;2},
  url = {https://pubs.usgs.gov/publication/70227466},
  note = {Source identifier: 70227466}
}