P. Ehlen, R. Zajac, and K. Rao. Proceedings of the Second International Workshop on Location and the Web (LocWeb 2009), page 17-19. Boston, Massachusetts, (April 2009)
J. Linebarger, A. Scholand, M. Ehlen, and M. Procopio. GROUP '05: Proceedings of the 2005 international ACM SIGGROUP conference on Supporting group work, page 51--60. New York, NY, USA, ACM Press, (2005)