Integrated Services Digital Network (ISDN) - Signalling System No. 7 (SS7); ISDN User Part (ISUP) version 4 for the international interface - Part 10: Subaddressing (SUB) supplementary service (ITU-T Recommendation Q.731, clause 8 (1992), modified) (Endorsement of the English version EN 300356-10 V 4.1.2 (2001-07) as German standard)