P. Resnick, N. Iacovou, M. Suchak, P. Bergstrom, and J. Riedl. CSCW '94: Proceedings of the 1994 ACM conference on Computer supported
cooperative work, page 175--186. New York, NY, USA, ACM, (1994)
B. Miller, J. Riedl, and J. Konstan. 1997 Annual Technical Conference, January 6--10, 1997. Anaheim, CA, USA, page 219--233. Berkeley, CA, USA, USENIX, (1997)