Quasiconformal homeomorphisms between Riemann surfaces
Ahlfors' disc theorem for Riemann covering surfaces is extended to normally exhaustible Klein coverings.
Due to a technical error, part of a sentence was omitted on the top of page 8. The first line should read: “where , or , means the number of folds of the covering ending at p, i.e. covering a neighbourhood of p in without covering p itself”.
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