@misc{indiciaed34a33f9939b,
  title = {Correlation of Permian and Pennsylvanian rocks from western Kansas to the Front Range of Colorado},
  author = {John Charles Maher and Jack B. Collins},
  year = {1952},
  doi = {10.3133/oc46},
  url = {https://pubs.usgs.gov/publication/oc46},
  note = {Source identifier: oc46}
}