@misc{indiciae2e1b1be41854,
  title = {40Ar/39Ar dates for the Spanish Peaks intrusions in south-central Colorado},
  author = {B.S. Penn and David A. Lindsey},
  year = {2009},
  doi = {10.2113/gsrocky.44.1.17},
  url = {https://pubs.usgs.gov/publication/70208501},
  note = {Source identifier: 70208501}
}