1. Proceedings of the International Conference on: High Temperature Superconductors and Materials and Mechanisms of Superconductivity, Interlaken, 1988. Editors: M�ller, J., Olsen, J.L. (eds.). Physica C154?155 (1988)
2. For reviews of various results of high energy spectroscopies see e.g.: Wendin, G.: J. Phys. (Paris) Coloq. C9, 1987; Fuggle, J.C., Fink, J., N�cker, N.: Int. J. Mod. Phys. B, preprint 1988; Ramaker, D.E.: Adv. Chem. Phys. preprint 1988; Hass, K.C.: Solid State Phys.42 (1989)
3. N�cker, N., Fink, J., Fuggle, J.C., Durham, P.J., Temmerman, W.M.: Phys. Rev. B37, 6827 (1988)
4. H�fner, S.: Z. Phys. B-Condensed Matter58, 1 (1985); ibid. H�fner, S.: Z. Phys. B-Condensed Matter61, 135 (1985)
5. Bednorz, J.G., M�ller, K.A.: Z. Phys. B-Condensed Matter63, 189 (1986)