Component-Based Entity Systems in Spielen (text is in German)
The text is a very nice description of entity component systems, and quite similar to my recent news post More about Component Systems of January 2014 (see our News and Announcements for related posts and follow-ups).
The authors present a few additional details that are slightly different from ours, but the crucial elements, namely using aggregation rather than class hierarchies for feature "management", and using flexible means for managing each component's data (variables), exactly match ours.
In summary, the text is a great additional view on component systems. Comparing its details to ours is interesting and provides additional perspective and insights.