The site presents a hierarchical organization for Wikipedia articles with respect to their semantic similarity and provides search and navigation facilities over the hierarchy. The hierarchy is constructed as a recursive division of the English Wikipedia graph into dense subgraphs (graph communities) and can be considered as an extension to the Wikipedia category structure. Unlike Wikipedia categories that are primarily authored by humans, the community hierarchy is fully automatic, purely link-based and reflects the global link structure of Wikipedia.
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. The Semantic Web: Research and Applications, volume 4011 of Lecture Notes in Computer Science, page 411--426. Berlin/Heidelberg, Springer, (June 2006)
R. Baeza-Yates, P. Boldi, and C. Castillo. SIGIR '06: Proceedings of the 29th annual international ACM SIGIR conference on Research and development in information retrieval, page 308--315. New York, NY, USA, ACM Press, (2006)