Home location register specification : ETSI technical specification GSM 11.31: release note: version 3.2.1 / European Telecommunications Standards Institute
Visitor location register specification : ETSI technical specification GSM 11.32: release note: version 3.2.1 / European Telecommunications Standards Institute
Performance data measurements : recommendation GSM 12.04: release note: version 3.2.0 / European Telecommunications Standards Institute
Estatísticas dos transportes e comunicações / ed. Instituto Nacional de Estatística