@misc{indiciae087f7085bdde,
  title = {Maps showing distribution, composition, and age of early and middle Cenozoic volcanic centers in Colorado and Utah},
  author = {R. G. Luedke},
  year = {1993},
  doi = {10.3133/i2291b},
  url = {https://pubs.usgs.gov/publication/i2291B},
  note = {Source identifier: i2291B}
}