S. Braun, A. Schmidt, A. Walter, and V. Zacharias. Good Tags and Bad Tags - Social Tagging in der Wissensorganisation, volume 47 of Medien in der Wissenschaft, Waxmann, (2008)
V. Zacharias, S. Braun, and A. Schmidt. Handbook of Research on Web 2.0, 3.0 and X.0: Technologies, Business, and Social Applications, IGI Global, (2009)