@misc{indiciae9a9709beaef7,
  title = {Determination of thorium in the parts per million range in rocks},
  author = {Harry Levine and F. S. Grimaldi},
  year = {1957},
  doi = {10.3133/tei692},
  url = {https://pubs.usgs.gov/publication/tei692},
  note = {Source identifier: tei692}
}