On a problem about the Epstein zeta-function

Let be a positive definite binary quadratic form with determinant αβ − δ 2 = 1. A special form of this kind is We consider the Epstein zeta-function the series converging for . The function Z h ( s ) can be analytically continued over the whole s -plane and it is regular except for a simple pole with residue π at s = 1.