1. 1 Except for some of the isotopes of uranium. National Bureau of Standards, Circular 499. The half-life has been recently recently redetermined by Lounsbury and Hawkins, Chalk River, Canada. They found (3.08 ± .03) × 105 years. Private communication.
2. 2 Neutron Cross Sections, AECU 2040.
3. Interpretation of Cosmic-Ray Phenomena
4. Neutron Production at Mountain Altitudes