ITU-T Q.954.2-1995
综合数字业务网: 条款2-三方业务-NO.1数字用户信令系统
Integrated Services Digital Network (ISDN) - Stage 3 Description for Multiparty Supplementary Services Using DSS 1 Clause 2 - Three Party (3PTY) - Digital Subscriber Signalling System No. 1 (Study Group 11) 39 pp