- Author: Thomas Doktor, Carla Spies
- Language: German
- Year: 1997
- Author: Niklas Luhmann
- Language: German
- Year: 2000
- Author: Robert Walter Daniel, Franco Maltomini
- Language: English
- Year: 1990
- Author: Klaus-Michael Bogdal
- Language: German
- Year: 1991
- Author: Christoph Kuhlmann
- Language: German
- Year: 1999
- Author: Hans-Peter Müller Michael Schmid
- Language: German
- Year: 1998
- Author: Luhmann Niklas
- Language: German
- Year: 1995
- Author: Jürgen Mackert Hans-Peter Müller (Hrsg.)
- Language: German
- Year: 2000
