J. Binder, A. Howes, and A. Sutcliffe. CHI '09: Proceedings of the 27th international conference on Human factors in computing systems, page 965--974. New York, NY, USA, ACM, (2009)
A. Richter, and M. Koch. Proc. Intl. Conf. on the Design of Cooperative Systems 2008, page 87-98. Carry-le-Rouet, France, Institut d'Etudes Politiques d'Aix-en-Provence, (May 2008)