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(i) Tetragonal subgroups
The class contains the classes and . Maximal t subgroups belonging to these classes are read directly from the standard full symbol.
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(ii) Orthorhombic subgroups
In the orthorhombic subgroups, the symmetry elements belonging to directions [100] and [010] are the same, except that a glide plane b perpendicular to [100] is accompanied by a glide plane a perpendicular to [010].
These examples show that P- and C-cell, as well as I- and F-cell descriptions of tetragonal groups have to be considered together.
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(iii) Monoclinic subgroups
Only space groups of classes 4, and have maximal monoclinic t subgroups.
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