1. Migdal, A.B.: JETP34, 1184 (1972); Rev. Mod. Phys.50, 107 (1978)
2. Sawyer, R.F., Scalapino, D.J.: Phys. Rev. D7, 953 (1972)
3. Au, C.K., Baym, G.: Nucl. Phys. A236, 1 (1976)
4. Brown, G.E., Weise, W.: Phys. Reports27 C, 1 (1976)
5. B�ckman, S.O., Weise, W., in: Mesons in Nuclei, Rho, M., Wilkinson, D.H. (eds.), pp. 1096. Amsterdam: North Holland Publ. 1979