L. Denoue, J. Adcock, S. Carter, and G. Golovchinsky. HT '09: Proceedings of the Twentieth ACM Conference on Hypertext and Hypermedia, New York, NY, USA, ACM, (July 2009)
K. Luther, S. Counts, K. Stecher, A. Hoff, and P. Johns. CHI '09: Proceedings of the 27th international conference on Human factors in computing systems, page 239--248. New York, NY, USA, ACM, (2009)
K. Everitt, S. Klemmer, R. Lee, and J. Landay. CHI '03: Proceedings of the SIGCHI conference on Human factors in computing systems, page 553--560. New York, NY, USA, ACM, (2003)
J. Tang, and S. Minneman. CHI '91: Proceedings of the SIGCHI conference on Human factors in computing systems, page 315--322. New York, NY, USA, ACM, (1991)The idea was evolved in 1991! Why didn't it get a successful product??.