@misc{indiciaec113cefb8b6a,
  title = {Gypsum-karst collapse in the Black Hills, South Dakota-Wyoming, USA},
  author = {Jack B. Epstein},
  year = {2016},
  doi = {10.3986/ac.v29i2.452},
  url = {https://pubs.usgs.gov/publication/70231228},
  note = {Source identifier: 70231228}
}