B. Sigurbjörnsson, and R. van Zwol. WWW '08: Proceeding of the 17th international conference on World Wide Web, page 327--336. New York, NY, USA, ACM, (2008)
P. Heymann, G. Koutrika, and H. Garcia-Molina. WSDM '08: Proceedings of the international conference on Web search and web data mining, page 195--206. New York, NY, USA, ACM, (2008)
C. Yeung, N. Gibbins, and N. Shadbolt. Proceedings of the 6th International Semantic Web Conference and 2nd Asian Semantic Web Conference (ISWC/ASWC2007), Busan, South Korea, volume 4825 of LNCS, page 960--964. Berlin, Heidelberg, Springer Verlag, (November 2007)
L. von Ahn, and L. Dabbish. CHI '04: Proceedings of the SIGCHI conference on Human factors in computing systems, page 319--326. New York, NY, USA, ACM Press, (2004)