@misc{indiciaee61a9de515a0,
  title = {Structure-contour map of the Montana plains},
  author = {C. E. Dobbin and C. E. Erdmann},
  year = {1946},
  doi = {10.3133/ofr4633},
  url = {https://pubs.usgs.gov/publication/ofr4633},
  note = {Source identifier: ofr4633}
}