D. Huynh, D. Karger, and R. Miller. Proceedings of the 16th international conference on World Wide Web, page 737--746. Banff, Alberta, Canada, ACM, (2007)
D. Johnson, and T. Jankun-Kelly. Proceedings of graphics interface 2008, page 163--168. Toronto, Ont., Canada, Canada, Canadian Information Processing Society, (2008)