DIN EN 300090:2001
综合业务数字网(ISDN).呼叫线路识别限制补充业务.业务说明
Integrated Services Digital Network (ISDN) - Calling Line Identification Restriction (CLIR) supplementary service - Service description (Endorsement of the English version EN 300090 V 1.2.1 (2000-12) as German Standard)