ETSI TS 129 060 Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); General Packet Radio Service (GPRS); GPRS Tunnelling Protocol (GTP) across the Gn and Gp Interface (3G TS 29.060 version 3.5.0 Release 1999)

standard by European Telecommunications Standards Institute, 06/01/2000