Flat 2-orbifold groups
This is a summary of some of the basic facts about flat 2-orbifold groups, otherwise known as 2-dimensional crystallographic groups. We relate the geometric and topological presentations of these groups, and consider structures corresponding to decompositions of the orbifolds as fibrations or as unions. All this material is well known; the only novelty here is perhaps in bringing this material together.Keywords: crystallographic; flat; orbifold; wall-paper group.
AMS Subject Classification: Primary 57M05; secondary 57M50.
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