Chapter in Encyclopedia of interaction design
Professor Victor Kaptelinin has published a chapter on Activity Theory in the Encyclopedia of interaction design
The encyclopedia is an open access initiative and includes contributions from renowned researchers in Human computer interaction and interaction design.
The full reference and link to the chapter:
Kaptelinin, Victor (2012): Activity Theory. In: Soegaard, Mads and Dam, Rikke Friis (eds.). "Encyclopedia of Human-Computer Interaction". The Interaction-Design.org Foundation . Available online athttp://www.interaction-design.org/encyclopedia/activity_theory.html