Hey, I have been looking around for a good resource explaining the analytic properties of Feynman diagrams and their resulting amplitudes. I think I understand in general what to expect (branch cuts for multiparticle states, poles for single particle states and bound states), but I'm not sure exactly how to see this from the mathematical expressions. Does any of you know a good resource explaining how these properties can be seen from the calculations? Preferable a source with many examples (including if possible examples from Non-Abelian gauge theories - specifically QCD). Thanks!