1. The e-mail reference interview;Abels;Reference Quarterly,1996
2. Adamic, L. A., Zhang, J., Bakshy, E., & Ackerman, M. S. (2008). Knowledge sharing and Yahoo! Answers: Everyone knows something. In Proceedings of the 2008 International World Wide Web Conference (pp. 665–674). Beijing: ACM.
3. Agichtein, E., Castillo, C., Donato, D., Gionides, A., & Mishne, G. (2008). Finding high-quality content in social media. In Proceedings of Web Search and Web Data Mining 2008 (pp. 183–193). Palo Alto, CA: ACM.
4. Answerbag (2009). About us. Retrieved July 5, 2009, from http://www.answerbag.com/about/
5. General system theory: Foundations, developments, applications.;Bertalanffy,1968