@misc{indiciae665e93ea2580,
  title = {Average elevation map of the conterminous United States (Gilluly averaging method)},
  author = {W.H. Diment and T. C. Urban},
  year = {1981},
  doi = {10.3133/gp933},
  url = {https://pubs.usgs.gov/publication/gp933},
  note = {Source identifier: gp933}
}