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paper

The group structure of the normalizer of $Γ_0(N)$

arXiv:math/0701636

Abstract

We determine the group structure of the normalizer of $Γ_0(N)$ in $SL_2(\R)$ modulo $Γ_0(N)$. These results correct the Atkin-Lehner statement at the paper Hecke operators of $Γ_0(N)$.