N. Xia, J. Jiang, and Y. Hu. Proceedings or the IEEE/WIC/ACM International Conference on Intelligent Agent Technology, page 475--478. Beijing, China, IEEE, (2004)
Y. Hu, Y. Koren, and C. Volinsky. Proceedings of the 2008 Eighth IEEE International Conference on Data Mining, page 263--272. Washington, DC, USA, IEEE Computer Society, (2008)