@misc{indiciae8d64f9d9e739,
  title = {U-Pb dating of uranium deposits in collapse breccia pipes of the Grand Canyon region},
  author = {K.R. Ludwig and K. R. Simmons},
  year = {1992},
  doi = {10.2113/gsecongeo.87.7.1747},
  url = {https://pubs.usgs.gov/publication/70016841},
  note = {Source identifier: 70016841}
}