(1) Triclinic space groups:
(i) ,
(ii) ,
(iii) ,
(iv) Acentring,
(v) Bcentring,
(vi) Ccentring,
(vii) Fcentring.

(2) Monoclinic space groups:
(a) with P lattice, unique axis b:
(i) ,
(ii) ,
(iii) ,
(iv) Bcentring,
(v) Ccentring,
(vi) Acentring,
(vii) Fcentring.

(b) with P lattice, unique axis c:
(i) ,
(ii) ,
(iii) ,
(iv) Ccentring,
(v) Acentring,
(vi) Bcentring,
(vii) Fcentring.

(c) with C lattice, unique axis b: There are three sublattices of index 2 of a monoclinic C lattice. One has lost its centrings such that a P lattice with the same unit cell remains. The subgroups with this sublattice are listed under `Loss of centring translations'. The block with the other two sublattices consists of , Ccentring and Icentring. The sequence of the subgroups in this block is determined by the spacegroup number of the subgroup.
(d) with A lattice, unique axis c: There are three sublattices of index 2 of a monoclinic A lattice. One has lost its centrings such that a P lattice with the same unit cell remains. The subgroups with this sublattice are listed under `Loss of centring translations'. The block with the other two sublattices consists of , Acentring and Icentring. The sequence of the subgroups in this block is determined by the No. of the subgroup.

(3) Orthorhombic space groups:
(a) Orthorhombic space groups with P lattice: Same sequence as for triclinic space groups.
(b) Orthorhombic space groups with C (or A) lattice: Same sequence as for monoclinic space groups with C (or A) lattice.
(c) Orthorhombic space groups with I and F lattice: There are no subgroups of index 2 with enlarged unit cell.

(4) Tetragonal space groups:
(5) For trigonal and hexagonal space groups, holds.
For rhombohedral space groups referred to hexagonal axes, , , or , , holds.
For rhombohedral space groups referred to rhombohedral axes, , , or , , , Fcentring holds.
(6) Only cubic space groups with a P lattice have subgroups of index 2 with enlarged unit cell. For their lattices the following always holds: , , , Fcentring.
