1. Barnett, Bell, Luce, Shipley, and Simon,Proceedings of the Second International Conference on Peaceful Uses of Atomic Energy, Geneva(1958), Paper No. 344.
2. R. F. Post,Proceedings of the Second International Conference on Peaceful Uses of Atomic Energy, Geneva(1958),Paper No. 333.
3. H. Bethe and J. Ashkin,Experimental Nuclear Physics, Part II, (John Wiley and Sons, Inc., New York 1953), p. 166.