@misc{indiciaeb110fa4b3854,
  title = {Stratigraphy of the Pierre Shale, Valley City and Pembina Mountain areas, North Dakota},
  author = {J. R. Gill and W. A. Cobban},
  year = {1965},
  doi = {10.3133/pp392a},
  url = {https://pubs.usgs.gov/publication/pp392A},
  note = {Source identifier: pp392A}
}