D. Zühlke. Nutzergerechte Entwicklung von Mensch-Maschine-Systemen: Useware-Engineering für technische Systeme, chapter 7, Springer, Berlin, 2 edition, (2012)
P. Gebhard, and M. Klesen. Intelligent Virtual Agents: 5th International Working Conference, IVA 2005, Kos, Greece, volume 3661 of Lecture Notes in Artificial Intelligence, Springer, Berlin, (2005)