Qian Zhang 0001 Chuanxiong Guo Zihua Guo Wenwu Zhu 0001 Efficient mobility management for vertical handoff between WWAN and WLAN. 102-108 2003 41 IEEE Commun. Mag. 11 https://doi.org/10.1109/MCOM.2003.1244929 db/journals/cm/cm41.html#ZhangGG003