Private Telecommunication Network (PTN) - Specification, functional model and information flows - Call intrusion supplementary service; English version ETS 300425:1995
Private Integrated Services Network (PISN) - Specification, functional model and information flows - Call intrusion supplementary service [ISO/IEC 14845 (1996), modified] (Endorsement of the English version EN 300425 V 1.2.1 (1999-03) as German standard)— 1 стр.
