• The authors are with the Human Computer Interaction Institute, School of Computer Science, Carnegie Mellon University, 500 Forbes Ave., Pittsburge, PA 15213. E-mail: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org.
Manuscript received 16 Sept. 2008; revised 28 Dec. 2008; accepted 7 Jan. 2009; published online 16 Jan. 2009.
For information on obtaining reprints of this article, please send e-mail to: email@example.com, and reference IEEECS Log Number TLTSI-2008-09-0089.
Digital Object Identifier no. 10.1109/TLT.2009.8.