  Let $F(s)=\sum_n a_n/\lambda_n^s$ be a general Dirichlet series which is
absolutely convergent on $\Re(s)>1$. Assume that $F(s)$ has an analytic
continuation and satisfies a growth condition, which gives rise to certain
invariants namely the degree $d_F$ and conductor $\alpha_F$. In this paper, we
show that there are at most $2d_F$ general Dirichlet series with a given degree
$d_F$, conductor $\alpha_F$ and residue $\rho_F$ at $s=1$. As a corollary, we
get that elements in the extended Selberg class with positive Dirichlet
coefficients are determined by their degree, conductor and the residue at
$s=1$.
