N. Agarwal, H. Liu, L. Tang, und P. Yu. WSDM '08: Proceedings of the international conference on Web search and web data mining, Seite 207--218. New York, NY, USA, ACM, (2008)
C. Ahlberg, C. Williamson, und B. Shneiderman. CHI '92: Proceedings of the SIGCHI conference on Human factors in computing systems, Seite 619--626. New York, NY, USA, ACM Press, (1992)