@misc{indiciaef3db93f716d5,
  title = {Results of spirit leveling in Pennsylvania, 1899 to 1911, inclusive},
  author = {Robert Bradford Marshall},
  year = {1912},
  doi = {10.3133/b515},
  url = {https://pubs.usgs.gov/publication/b515},
  note = {Source identifier: b515}
}