Quasi-particle description of strongly interacting matter: Towards a foundation M. Bluhm, B. Kämpfer, R. Schulze and D. Seipt Eur. Phys. J. C, 49 1 (2007) 205-211 Published online: 21 October 2006 DOI: 10.1140/epjc/s10052-006-0056-y