TITLE: looking for reference on dihedral, tetrahedral, or octahedral forms
QUESTION [5 upvotes]: I am looking for a reference on dihedral, tetrahedral, or octahedral forms. As far as I read, they are some cuspidal automorphic forms on $GL(2)$ induced from $GL(1)$. Dihedral is from $GL(1)/K$ to $GL(2)/\mathbb{Q}$, where $K$ is a quadratic extension of $\mathbb{Q}$. But is this the same for tetrahedral or octahedral forms? What's their constructions?

REPLY [3 votes]: I think a basic reference is Serre's paper "Modular forms of weight one and Galois representations” in Algebraic Number Fields, ed. by A. Frohlich,
 ̈Academic Press, 1977, 193–268; also in OEuvres, Vol. III, Springer-
Verlag, Berlin, 1986, 292–367.