reference needed: Dirichlet L-functions

Where is the logarithmic derivative at $s=0$ of the L-function of a Dirichlet character computed? Many people cite the Hurwitz formula but I was unable to find a suitable reference.

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Look here: math.stackexchange.com/questions/112688/…. –  Dietrich Burde Jan 21 '14 at 12:34
In this post there is a formula for the logarithmic derivative but no further reference (only the computation of the value $L(0, \chi)$ is discussed). I already know the formula. What I want is a reference in which it is proved. –  carapace Jan 21 '14 at 13:43
See Lemma 3.1 in math.uiuc.edu/~berndt/articles/az4.pdf‎ with $k=2$. –  Dietrich Burde Jan 21 '14 at 13:53