Signalling interworking for supplementary services : recommendation GSM 09.11: release note: version 3.0.1 / European Telecommunications Standards Institute
Mobile station conformity specifications : recommendation GSM 11.10: update note: version 3.11.0 / European Telecommunications Standards Institute
Specifications of the SIM-ME interface : ETSI technical specification GSM 11.11: release note: version 3.12.0 / European Telecommunications Standards Institute
The GSM base station system : equipment specification: recommendation GSM 11.20: update note: version 3.10.0 / European Telecommunications Standards Institute