1. Glatz, F., Siefert, J., Betz, P., Bitterwolf, E., Burkard, A., Heidinger, F., Kern, Th., Lehmann, R., Norbert, S., Röpke, H.: Z. Phys. A. ? Atoms and Nuclei303, 239 (1981)
2. Wildenthal, B.H.: Progress in Particle and Nuclear Physics 11. Wilkinson, D.H. (ed.), p. 1. New York: Plenum Press 1984
3. Wildenthal, B.H.: Elementary modes of nuclear excitations. Broglia, R., Bohr, A. (eds.), p. 383. Amsterdam: North Holland Publ. Co. 1977
4. Alexander, T.K., Broude, C., Ferguson, A.J., Kuehner, J.A., Litherland, A.E., Ollerhead, R.W., Smulders, P.J.M.: Can. J. Phys.47, 651 (1969)
5. Neal, F., Lam, S.T.: Bull. Am. Phys.19, 74 (1974)