Modular forms of genus 2 and weight 1
The author proves, that any Siegel modular form of genus two, which is a cusp form of weight 1 with respect to some congruence subgroup of type \(\Gamma_ 0(N)\) and some nebentypus character \(\chi\), is a linear combination of theta series attached to binary quadratic forms. This is an analog of the results of Serre and Stark on elliptic modular forms of weight 1/2, and strengthens earlier results of Andrianov.
scientific article; zbMATH DE number 4216036