R. Amant, T. Horton, and F. Ritter. CHI '04: Proceedings of the SIGCHI conference on Human factors in computing systems, page 343-350. New York, NY, USA, ACM Press, (2004)
H. Jørgensen. GROUP '01: Proceedings of the 2001 International ACM SIGGROUP Conference on Supporting Group Work, page 32--41. New York, NY, USA, ACM Press, (2001)