A. Wang. Data and Applications Security and Privacy XXIV, том 6166 из Lecture Notes in Computer Science, глава 25, Springer Berlin / Heidelberg, Berlin, Heidelberg, (2010)
W. Reinhardt, M. Ebner, G. Beham, и C. Costa. Hornung-Pr\ähauser, V., Luckmann, M.(Hg.): 5th EduMedia conference, Salzburg, стр. 145--156. Citeseer, (2009)