@misc{indiciae03c6a311ea09,
  title = {Geologic and structure map of the southern part of the Powder River basin, Converse, Niobrara, and Natrona counties, Wyoming},
  author = {G. H. Horn},
  year = {1975},
  doi = {10.3133/i877},
  url = {https://pubs.usgs.gov/publication/i877},
  note = {Source identifier: i877}
}