Private Integrated Services Network (PISN) - Inter-exchange signalling protocol - Generic functional protocol for the support of supplementary services [ISO/IEC 11582 (1995), modified]; English version ETS 300239:1995
Private Integrated Services Network (PISN) - Inter-exchange signalling protocol - Generic functional protocol for the support of supplementary services [ISO/IEC 11582 (2002) modified] (Endorsement of the English version EN 300239 V1.3.1 (2003-06) as German standard)— 2 стр.