The space group reference in its simplest form can be just the number 1 to 230, as described for SymCIF:_space_group.IT_number and referred as the "assigned International Tables number", or more commonly, the "IT number", "space group number", or just "SG" herein. It is important to note that this number in CLEG notation also specifically refers to the International Table reference setting for that space group type, which is a unique setting for each of the 230 crystallographic space-group types.