M. Grahl, A. Hotho, and G. Stumme. 7th International Conference on Knowledge Management (I-KNOW '07), page 356-364. Graz, Austria, Know-Center, (September 2007)
A. Dattolo, F. Tomasi, and F. Vitali. Handbook of Research on Web 2.0, 3.0 and X.0: Technologies, Business, and Social Applications, chapter 20, IGI Global, Hershey, PA, (2010)
C. man Au Yeung, N. Gibbins, and N. Shadbolt. HT '09: Proceedings of the Twentieth ACM Conference on Hypertext and Hypermedia, New York, NY, USA, ACM, (July 2009)
A. Dattolo, F. Ferrara, and C. Tasso. Proc. of the 3rd International Conference on Human System Interaction - HSI'2010, page 548-555. Rzeszow, Poland, IEEE press, (May 2010)