1. See, for example, the other contributions to this volume, and the references therein.
2. I. Tserruya, this volume, Sect. 4.2.
3. Joseph I. Kapusta and Charles Gale, Finite-Temperature Field Theory: Principles and Applications, Cambridge University Press (Cambridge, 2006).
4. Alexander L. Fetter and John Dirk Walecka, Quantum Theory of Many-Particle Systems, McGraw-Hill (New York, 1971).
5. P. Braun-Munzinger, K. Redlich and J. Stachel, arXiv:nucl-th/0304013.