@misc{indiciae52888e455ddb,
  title = {Preliminary map showing sand and gravel deposits of Nebraska},
  author = {R. A. Weeks and David M. Larrabee},
  year = {1948},
  doi = {10.3133/mb7},
  url = {https://pubs.usgs.gov/publication/mb7},
  note = {Source identifier: mb7}
}