1. M. Day, J. Rosenberg, H. Sugano, A Model for Presence and Instant Messaging (2000). URL http://portal.acm.org/citation.cfm?id=RFC2778.
2. H. Sugano, S. Fujimoto, G. Klyne, A. Bateman, W. Carr, J. Peterson, Presence information data format (pidf), Internet RFC 3863 (August 2004).
3. H. Schulzrinne, V. Gurbani, P. Kyzivat, J. Rosenberg, RPID: Rich Presence Extensions to the Presence Information Data Format (PIDF), RFC 4480 (Proposed Standard) (July 2006). URL http://www.ietf.org/rfc/rfc4480.txt.
4. B. Schilit, N. Adams, R. Want, Context-aware computing applications, in: Proceedings of the 1994 First Workshop on Mo- bile Computing Systems and Applications, WMCSA 94, IEEE Computer Society, Washington, DC, USA,;1; 1994, pp. 85-90. doi:10.1109/WMCSA. 1994.16. URL http://dx.doi.org/10.1109/WMCSA.;1; 1994.16.
5. M. J. Pascoe, Adding generic contextual capabilities to wearable computers, in: Proceedings of the 2nd IEEE International Symposium on Wearable Computers, ISWC 98, IEEE Computer Society, Washington, DC, USA,;1; 1998, pp. 92–URL http://dl.acm.org/citation.cfm?id=857199.858020.