1. Weiser, M.: The computer for the twenty-first century. Scientific American, 94–104 (September 1991)
2. Brock, D.: The networked physical world, proposals for engineering the next generation of computing, commerce and automatic-identification. Auto-ID Centre Whitepaper (January 2001)
3. Magrassi, P.: A world of smart objects: The role of auto identification technologies. Strategic Analysis Report, Gartner (2001)
4. Brock, D.: The physical markup language. Auto-ID Centre Whitepaper (February 2001)
5. Kindberg, T., Barton, J., Morgan, J., Becker, G., Caswell, D., Debaty, P., Gopal, G., Frid, M., Krishnan, V., Morris, H., Schettino, J., Serra, B., Spasojevic, M.: People, places, things: Web presence for the real world. In: 2000 Third IEEE Workshop on Mobile Computing Systems and Applications, pp. 19–28 (2000)