1. For recent developments see Quark Matter 96, Proc. 12th Int. Conf. on Ultra-Relativistic Nucleus-Nucleus Collisions, Heidelberg, Germany, 1996, Nucl. Phys. A 610, and references therein.
2. Hadrons in Nuclear Matter, H. Feldmaier, W. Nörenberg (Ed.), GSI, Darmstadt, 1995, Proc. Int. Workshop XXIII on Gross Properties of Nuclei and Nuclear Excitations, Hirschegg, Austria, 1995.
3. CERES Collaboration, G. Agakichiev et al., Phys. Rev. Lett. 75 (1995).
4. HELIOS/3 Collab., M. Masera et al., Nucl. Phys. A 590 (1995) 3c.
5. Effects of in-medium vector meson masses on low-mass dileptons from SPS heavy-ion collisions