Integrated Services Digital Network (ISDN); user-network interface data link layer specification; application of CCITT recommendations Q.920/I.440 and Q.921/I.441; english version ETS 300125:1991
综合业务数字网(ISDN);用户网络接口数据链路层规范;CCITT建议Q.920/I.440和Q.921/I.441的应用;英文版ETS 300125:1991