1. J. M. Eisenberg and W. Greiner, Nuclear Theory (North-Holland, Amsterdam, 1970), Vol. 1.
2. A. S. Davydov and G. F. Fillipov, Nucl. Phys. 8, 237 (1958).
3. A. S. Davydov, Excited States of Nuclei (Atomizdat, Moscow, 1967) [in Russian].
4. V. V. Strutinskiĭ, Sov. J. Nucl. Phys. 3, 449 (1966).
5. D. R. Inglis, Phys. Rev. 97, 701 (1955).