I'm trying to find the momentum space integral representation of the below Feynman Diagram, but am having troubles with the fact that there are two loops within the system.

The main question I have is how to deal with a 2 loop system in Feynman Diagrams. If I have that, I can solve the rest of my problems myself!

Feynman Diagram of QED 2 loop system

Starting from the right hand side and going in an anti-clockwise loop, I get (Line breaks are required to be a bit more readable)

$$ \int \frac{d^4 k_1}{(2 \pi)^4} \int \frac{d^4 k_2}{(2 \pi)^4}\epsilon^*_\mu (q) \\Tr \left[ (-ie\gamma^\mu) \frac{i({\gamma^\alpha q_\alpha} + \gamma^\alpha {{k_1}_\alpha} + m)}{(q + k_1)^2 - m^2 + i\epsilon}(-ie\gamma^\nu) \frac{i(\gamma^\alpha q_\alpha + \gamma^\alpha {k_2}_\alpha + m)}{(q + k_2)^2 - m^2 + i\epsilon}\\(-ie\gamma^\sigma) \frac{i(\gamma^\alpha{k_2}_\alpha + m)}{(k_2)^2 - m^2 + i\epsilon} (-ie\gamma^\rho) \frac{\gamma^\alpha{k_1}_\alpha + m}{(k_1)^2 - m^2 + i\epsilon} \right] \\ \frac{-i(g_{\rho\nu} - \frac{(k_1 - k_2)_\rho (k_1 - k_2)_\nu}{(k_1 - k_2)^2} )}{(k_1 - k_2)^2 + i\epsilon} \epsilon_\sigma (q) $$


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