@misc{indiciae84b393479d48,
  title = {Subsurface stratigraphy of the Heath shale and Amsden formation in central Montana},
  author = {C.L. Nieschmidt},
  year = {1953},
  doi = {10.3133/oc50},
  url = {https://pubs.usgs.gov/publication/oc50},
  note = {Source identifier: oc50}
}