1. F. L. Shapiro et al, Preprint P3-4127, Joint Institute of Nuclear Research, Dubna, USSR, 1968; Sov. Phys. JETP Lett.,9, 23, 1969.
2. A. Steyerl, Phys. Lett.,29B, 33, 1969.
3. A. P. Serebrov et al, Sov. Phys. JETP Lett.,44, 344, 1986.
4. A. Steyerl et al, Phys. Lett.,116A, 347, 1986.
5. V. F. Turchin, Slow Neutrons, Moscow, 1963.