ITU-T X.2-2000
公用数据网和ISDN的国际数据传输业务和任选的用户设施.系列X-业务与设施.第7研究组.第27页
International Data Transmission Services and Optional User Facilities in Public Data Networks and ISDNs Series X: Data Networks and Open System Communications Public Data Networks - Services and Facilities Study Group 7; 27 pp