1. K. Samsahl, AE-168, Stockholm, 1964.
2. D. Comar, Nucleonics, 24 (1966) No. 11, 54.
3. J. Schumacher, W. Maier-Borts, Kerntechnik, 14 (1972), 165.
4. L. O. Plantin, STI/PUB 310, IAEA, Bled, April 1952, p. 73.
5. R. E. Jervis, K. Y. Wong, STI/PUB 155, IAEA, Vienna, 1967, p. 137.