R. Torres, S. McNee, M. Abel, J. Konstan, and J. Riedl. Proceedings of the 4th ACM/IEEE-CS Joint Conference on Digital Libraries, page 228--236. New York, NY, USA, ACM, (2004)
A. Geyer-Schulz, A. Neumann, and A. Thede. Research and Advanced Technology for Digital Libraries, volume 2769 of Lecture Notes in Computer Science, Springer, Berlin/Heidelberg, (2003)
Z. Huang, W. Chung, T. Ong, and H. Chen. Proceedings of the 2Nd ACM/IEEE-CS Joint Conference on Digital Libraries, page 65--73. New York, NY, USA, ACM, (2002)