ETSI technical specification GSM 11.10 : release note: mobile station conformity specifications / European Telecommunication Standards Institute
ETSI technical specification GSM 11.20 : update note : the GSM base station system: equipment specificationf / European Telecommunication Standards Institute
ETR 010 : ISDN standards management (ISM): the ETSI basic guide on the european integrated services digital network / European Telecommunications Standards Institute
ETR 011 : network aspects: the relationship between network component performance and the overall network performance / European Telecommunications Standards Institute