1. Brown, G. S. (1971) Laws of Form. London: George Allen & Unwin.
2. Madsen, K. H. (ed.) (2002) Production Methods: Behind the Scenes of Virtual Inhabited 3D Worlds. London: Springer-Verlag.
3. Qvortrup, L. (ed.) (2001) Virtual Interaction: Interaction in Virtual Inhabited 3D Worlds. London: Springer-Verlag.
4. Qvortrup, L. (ed.) (2002) Virtual Space: Interaction in Virtual Inhabited 3D Worlds. London: Springer-Verlag.
5. Searle, J. R. (1970) Speech Acts. Cambridge: Cambridge University Press.