@misc{indiciae08569387baaa,
  title = {Summary of the geology, mineral resources, landscape geochemistry, and engineering geologic characteristics of the northern Powder River coal region, Montana: Geology and mineral resources},
  author = {W. J. Mapel and Vernon Emanuel Swanson},
  year = {1977},
  doi = {10.3133/ofr77292a},
  url = {https://pubs.usgs.gov/publication/ofr77292A},
  note = {Source identifier: ofr77292A}
}