International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2010 
International Tables for Crystallography (2010). Vol. B, ch. 4.6, p. 592
Figure 4.6.2.2 ^{a}Laboratory of Crystallography, Department of Materials, ETH Hönggerberg, HCI G 511, WolfgangPauliStrasse 10, CH8093 Zurich, Switzerland 

Figure 4.6.2.2
2D embedding of the sinusoidally modulated structure illustrated in Fig. 4.6.2.1. The correspondence between the actual displacement of an atom in the 1D structure and the modulation function defined in one additional dimension is illustrated in part (a). Adding to each atom its modulation function in this orthogonal dimension (perpendicular space ) yields a periodic arrangement in 2D space V, part (b). The MS results as a special section of the 2D periodic structure along the parallel space . It is obvious from a comparison of (b) and (c) that the actual MS is independent of the perpendicularspace scale. 