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On a subgroup of finite index in the $$n$$-dimensional discrete group of affine transformations. (Russian) Zbl 0722.20035
It is proved that if H is a subgroup of finite index in the group of affine motions G, then for G to be n-dimensional and discrete it is necessary and sufficient for H to be n-dimensional and discrete.
Reviewer: K.Riives (Tartu)
MSC:
 20H15 Other geometric groups, including crystallographic groups 20E07 Subgroup theorems; subgroup growth 57S30 Discontinuous groups of transformations 22E40 Discrete subgroups of Lie groups 51F15 Reflection groups, reflection geometries
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