The implementation of prepaid services over the SIP-based VoIP network. - Liang-Chang Yu; Tai-Liang Chen; Wei-Zu Yang (ITRE, 2005)

The Design of Multimedia Web-based Phone and Billing System with Freeware over the VoIP Network. - Wei-Zu Yang; Liang-Chang Yu; Po-Chou Chen; Tai-Liang Chen (SUTC (1), 2006)