ETS 300 133-3 : paging systems (PS): european radio message system (ERMES): part 3: network aspects: (annexes): ETS 300 133 -3 / European Telecommunications Standards Institute
ETS 300 133-6 : paging systems (PS): european radio message system (ERMES): part 6: base station conformance specification: ETS 300 133-6 / European Telecommunications Standards Institute
ETS 300 136 : integrated services digital network (ISDN): closed user group (CUG) supplementary service: service description / European Telecommunications Standards Institute
ETS 300 137 : integrated services digital network (ISDN): closed user group (CUG) supplementary service: functional capabilities and information flows / European Telecommunications Standards Institute