P. Persson, F. Espinoza, P. Fagerberg, A. S, and R. Cöster. in Kristina Höök, David Benyon and Alan Munro (eds), Readings in Social Navigation of Information Space, page 151--173. Springer, (2002)
P. Persson, F. Espinoza, and E. Cacciatore. CHI '01: CHI '01 extended abstracts on Human factors in computing systems, page 43--44. New York, NY, USA, ACM, (2001)