@misc{indiciae42ea620005e2,
  title = {Twelfth annual report of the United States Geological Survey, 1890-1891: Part 1-Geology},
  author = {J. W. Powell},
  year = {1891},
  doi = {10.3133/ar12},
  url = {https://pubs.usgs.gov/publication/ar12},
  note = {Source identifier: ar12}
}