@misc{indiciae5e5a960319a8,
  title = {Stratigraphy and geologic history of the Montana group and equivalent rocks, Montana, Wyoming, and North and South Dakota},
  author = {James R. Gill and William Aubrey Cobban},
  year = {1973},
  doi = {10.3133/pp776},
  url = {https://pubs.usgs.gov/publication/pp776},
  note = {Source identifier: pp776}
}