@misc{indiciae843e538c0e2e,
  title = {Landforms of the conterminous United States — A digital shaded relief portrayal},
  author = {Gail P. Thelin and Richard J. Pike},
  year = {1991},
  doi = {10.3133/i2206},
  url = {https://pubs.usgs.gov/publication/i2206},
  note = {Source identifier: i2206}
}