ETSI ETS 300 770-1 Broadband Integrated Services Digital Network (B-ISDN); Digital Subscriber Signalling System No. two (DSS2) protocol; Closed User Group (CUG) supplementary service; Part 1: Protocol specification [ITU-T Recommendation Q.2955.1 (1996), modified]

standard by European Telecommunications Standards Institute, 05/01/1998