T. Joachims, L. Granka, B. Pan, H. Hembrooke, und G. Gay. Proceedings of the 28th annual international ACM SIGIR conference on Research and development in information retrieval, Seite 154--161. New York, NY, USA, ACM, (2005)
B. Martins, H. Manguinhas, und J. Borbinha. Proceedings of the International Conference on Semantic Computing, Seite 1--9. IEEE Computer Society, (August 2008)