The Pew Research Center’s Internet & American Life Project, a nonprofit, nonpartisan research organization, provides free data and analysis on the social
N. Tintarev, und J. Masthoff. Proceedings of the 2007 IEEE 23rd International Conference on Data Engineering Workshop, Seite 801--810. Washington, DC, USA, IEEE Computer Society, (2007)
M. Yuen, L. Chen, und I. King. Proceedings of the International Conference on Computational Science and Engineering, CSE '09, 4, Seite 723--728. (August 2009)