@misc{indiciaed9f5677262e5,
  title = {Determination of thorium in the parts per million range in rocks},
  author = {H. Levine and F. S. Grimaldi},
  year = {1958},
  doi = {10.1016/0016-7037(58)90096-6},
  url = {https://pubs.usgs.gov/publication/70009846},
  note = {Source identifier: 70009846}
}