, 2013, System surfaces: there is never just only one structure, in B. Küppers, U. Hahn & S. Artmann (eds.), Evolution of semantic systems, Dordrecht, Springer, pp. 31-66.
, 2005, Knowledge + skills + "x", in K. Dieter Althoff, A. Dengel, R. Bergmann & M. Nick (eds.), Professional knowledge management, Berlin, Springer, pp. 32-47.
, 2000a, Data — information — knowledge: a trial of a technological enlightenment, in G. Banse, P. Machleidt, D. Uhl & C. J. Langenbach (eds.), Towards the information society, Dordrecht, Springer, pp. 109-124.