J. Yan, N. Liu, G. Wang, W. Zhang, Y. Jiang, und Z. Chen. Proceedings of the 18th international conference on World wide web, Seite 261--270. New York, NY, USA, ACM, (2009)
F. Portnoy, und G. Marchionini. Proceedings of the 28th of the international conference extended abstracts on Human factors in computing systems, Seite 4297--4302. New York, NY, USA, ACM, (2010)