Dalju Lee Jongmoon Baik QoS Protocol Verification using Petri-Net for Seamless Mobility in a Ubiquitous Environment: A Case Study. 617-622 2008 SNPD http://doi.ieeecomputersociety.org/10.1109/SNPD.2008.124 conf/snpd/2008 db/conf/snpd/snpd2008.html#LeeB08