1. Dehn, D.M., van Mulken, S.: The impact of animated interface agents: a review of empirical research. International Journal of Human-Computer Studies 52, 1–22 (2000)
2. Krämer, N.C., Bente, G.: Virtuelle Helfer: Embodied Conversational Agents in der Mensch-Computer-Interaktion. In: Bente, G., Krämer, N. C., Petersen, A. (eds.) Virtuelle Realitäten, Göttingen, Hogrefe, pp. 203-225 (2002)
3. van Mulken, S., André, E., Müller, J.: The persona effect: how substantial is it? In: Johnson, H., Nigay, L., Roast, C. (eds.) People and Computers XIII: Proceedings of HCI 1998, pp. 53–66. Springer, Berlin (1998)
4. Rickenberg, R., Reeves, B.: The effects of animated characters on anxiety, task performance, and evaluations of user interfaces. In: Letters of CHI 2000, pp. 49-56 (April 2000)
5. Bente, G., Krämer, N.C., Trogemann, G., Piesk, J., Fischer, O.: Conversing with electronic devices. An integrated approach towards the generation and evaluation of nonverbal behavior in face-to-face like interface agents. In: Heuer, A., Kirste, T. (eds.) Intelligent interactive assistance and mobile multimedia computing. Proceedings of the IMC 2000, Rostock, Neuer Hochschulschriftenverlag, pp. 67–76 (2001)