International
Tables for Crystallography Volume A Spacegroup symmetry Edited by M. I. Aroyo © International Union of Crystallography 2016 
International Tables for Crystallography (2016). Vol. A, ch. 2.1, p. 144

^{†}The twodimensional triple hexagonal cell h is an alternative description of the hexagonal plane net, as illustrated in Fig. 1.5.1.8
. It is not used for systematic planegroup description in this volume; it is introduced, however, in the sub and supergroup entries of the planegroup tables of International Tables for Crystallography, Vol. A1 (2010), abbreviated as IT A1. Planegroup symbols for the h cell are listed in Section 1.5.4
. Transformation matrices are contained in Table 1.5.1.1
.
^{‡}In the spacegroup tables (Chapter 2.3 ), as well as in IT (1935) and IT (1952), the seven rhombohedral R space groups are presented with two descriptions, one based on hexagonal axes (triple cell), one on rhombohedral axes (primitive cell). In the present volume, as well as in IT (1952) and IT A (2002), the obverse setting of the triple hexagonal cell R is used. Note that in IT (1935) the reverse setting was employed. The two settings are related by a rotation of the hexagonal cell with respect to the rhombohedral lattice around a threefold axis, involving a rotation angle of 60, 180 or 300° (cf. Fig. 1.5.1.6 ). Further details may be found in Section 1.5.4 and Chapter 3.1 . Transformation matrices are contained in Table 1.5.1.1 . ^{§}The triple hexagonal cell H is an alternative description of the hexagonal Bravais lattice, as illustrated in Fig. 1.5.1.8 . It was used for systematic spacegroup description in IT (1935), but replaced by P in IT (1952). It is used in the tables of maximal subgroups and minimal supergroups of the space groups in IT A1 (2010). Spacegroup symbols for the H cell are listed in Section 1.5.4 . Transformation matrices are contained in Table 1.5.1.1 . 