@misc{indiciae678e6165d01c,
  title = {A Rubidium-Strontium study of the Twilight Gneiss, West Needle Mountains, Colorado},
  author = {F. Barker and Z. E. Peterman and R.A. Hildreth},
  year = {1969},
  doi = {10.1007/bf00371424},
  url = {https://pubs.usgs.gov/publication/70001725},
  note = {Source identifier: 70001725}
}