1. AKG: AKG Acoustics GmbH—homepage. http://www.akg.com (2007). Accessed 26th Mar 2007. AKG Acoustics GmbH, Vienna, Austria
2. ARTracking: A.R.T. GmbH–Your expert for infrared optical tracking systems. Advanced Realtime Tracking GmbH, Weilheim i. OB, Germany. http://www.ar-tracking.de/ (2007) Accessed on March 26, 2007.
3. Bellotti, F., Berta, R., De Gloria, A., Margarone, M.: Supporting efficient design of mobile HCI. In: Proceedings of the Conference on Human Computer Interaction with Mobile Devices and Services (MobileHCI), pp. 241–255. Springer, Berlin (2003)
4. Bregman, A.S.: Auditory scene analysis: the perceptual organization of sound. MIT Press, Cambridge, Massachusetts, 792 pp. (1994)
5. Brusilovsky B.: Methods and techniques of adaptive hypermedia. User Model. User-Adapt. Interact. 6(2–3), 87–129 (1996)