CLEG notation also allows the use of symbols. Hall notation is particularly interesting in that it is directly decodable (by a machine!) to provide the full set of symmetry operation for any reference space group using well-established algorithms . The 230 reference setting Hall names are provided in the enumeration of possible values for SymCIF:_space_group.reference_setting and can also be found in the appendix in Table and at the CLEG GitHub site in data/cleg_settings.tab 14 (also included here as supporting information). CLEG notation uses square brackets to specify Hall space group reference settings. So, for example, the space group number "7" in a CLEG expression can be directly substituted with "[P -2yc]".