@misc{indiciae53f823ab1fb9,
  title = {The Martinsburg Formation (Middle and Upper Ordovician) in the Delaware Valley, Pennsylvania-New Jersey},
  author = {Avery Drake and Jack B. Epstein},
  year = {1967},
  doi = {10.3133/b1244h},
  url = {https://pubs.usgs.gov/publication/b1244H},
  note = {Source identifier: b1244H}
}