?. CHI '08: Proceeding of the twenty-sixth annual SIGCHI conference on Human factors in computing systems, page 1493--1496. New York, NY, USA, ACM, (2008)
B. Kay, and C. Watters. CHI '08: Proceeding of the twenty-sixth annual SIGCHI conference on Human factors in computing systems, page 1187--1196. New York, NY, USA, ACM, (2008)