@misc{indiciaeeb97b05e7e38,
  title = {Spirit leveling in Illinois, 1896-1942. Part 4, Northern Illinois},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1943},
  doi = {10.3133/b930d},
  url = {https://pubs.usgs.gov/publication/b930D},
  note = {Source identifier: b930D}
}