@misc{indiciae13bd99d60845,
  title = {Long-term highwall stability in the northwestern Powder River basin, Wyoming and Montana},
  author = {William K. Smith},
  year = {1980},
  doi = {10.3133/ofr801229},
  url = {https://pubs.usgs.gov/publication/ofr801229},
  note = {Source identifier: ofr801229}
}