Stefan Berger Henning Schulzrinne Stylianos Sidiroglou Xiaotao Wu Ubiquitous computing using SIP. 82-89 2003 conf/nossdav/2003 NOSSDAV http://doi.acm.org/10.1145/776322.776336 db/conf/nossdav/nossdav2003.html#BergerSSW03