@misc{indiciaee12ec5bcfaa4,
  title = {Results of spirit leveling in Michigan, 1911 and 1913},
  author = {Robert Bradford Marshall},
  year = {1914},
  doi = {10.3133/b559},
  url = {https://pubs.usgs.gov/publication/b559},
  note = {Source identifier: b559}
}