D. Morris, M. Morris, und G. Venolia. CHI '08: Proceeding of the twenty-sixth annual SIGCHI conference on Human factors in computing systems, Seite 1207--1216. New York, NY, USA, ACM, (2008)
R. Dachselt, M. Frisch, und M. Weiland. CHI '08: Proceeding of the twenty-sixth annual SIGCHI conference on Human factors in computing systems, Seite 1353--1356. New York, NY, USA, ACM, (2008)