@misc{indiciaeb42cbe32cec1,
  title = {Stability of highwalls in surface coal mines, western Powder Ridge Basin, Wyoming and Montana},
  author = {Fitzhugh T. Lee and William K. Smith and William Z. Savage},
  year = {1976},
  doi = {10.3133/ofr76846},
  url = {https://pubs.usgs.gov/publication/ofr76846},
  note = {Source identifier: ofr76846}
}