Electron anomalous magnetic moment

[Muoniex]

Hello there!
I'm trying to check the first order (1 loop) correction to the electron magnetic moment. I'm following Schwartz and Peskin, but both of them have a point where they hide the calculations, and I'm not sure if my calculations are correct.

The point is exactly this:

I don't know how to get from (17.23) to (17.24).
Do you know where can I check those steeps?
Thanks :)

 

[mfb]

There should be some publication where this was first derived.
Textbooks don't like to fill full pages with calculations barely anyone will follow.