@misc{indiciaea5d4d58550cf,
  title = {Swelling clays map of the conterminous United States},
  author = {W. W. Olive and A.F. Chleborad and C.W. Frahme and Julius Schlocker and R.R. Schneider and R. L. Schuster},
  year = {1989},
  doi = {10.3133/i1940},
  url = {https://pubs.usgs.gov/publication/i1940},
  note = {Source identifier: i1940}
}