T. Seyferth, A. Ritzhaupt, O. Singh, и R. Dedrick. Proceedings of the Association of Educational Communication and Technology, стр. 299-305. Anaheim, CA, Association of Educational Communication and Technology, (2007)
J. Völker, D. Vrandecic, Y. Sure, и A. Hotho. Proceedings of the European Semantic Web Conference, ESWC2007, том 4519 из Lecture Notes in Computer Science, Springer-Verlag, (июля 2007)