C. Blundell, E. Lewis, and M. Martin. TR-CIS-06-09. Department of Computer and Information Science, University of Pennsylvania, Philadelphia, PA, (April 2006)
S. Baumann, B. Jung, A. Bassoli, and M. Wisniowski. CHI '07 extended abstracts on Human factors in computing systems, page 1941--1946. New York, NY, USA, ACM, (2007)