@misc{indiciae195b92364a69,
  title = {Fission-track ages of zircons from three Tertiary porphyries near Tincup, Colorado},
  author = {Charles W. Naeser and Charles Cunningham},
  year = {1976},
  doi = {10.3133/ofr76831},
  url = {https://pubs.usgs.gov/publication/ofr76831},
  note = {Source identifier: ofr76831}
}