1. R. Marshak, Rev. Mod. Phys.,19, 185 (1947).
2. M. V. Veselov, in: Physics of Reactor Shielding [in Russian], Atomizdat, Moscow (1963), p. 89.
3. I. A. Kozachok, Dop. AN URSR, ser. B., No. 4, 328 (1968).
4. I. A. Kozachok and V. V. Kulik, Atomnaya Énergiya,32, No. 4, 307 (1972).
5. G. Ya. Rumyantsev, Atomnaya Énergiya,10, No. 1, 26 (1961).