Figure 7
Ditetragonal (bi)-pyramid {12l}ditetr, a combination of subforms{12l}tetr (shaded) and {21l}tetr (white). Subset {12l}tetr is mapped upon itself by the [Sigma]5 twin elements (diffraction case A, cf. Fig. 6[link]), whereas subset {21l}tetr has no twin-related coinciding counterpart and is `single' (`partial coincidence').  [article HTML]

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