quantum field theory - Is there a mistake in a QFT textbook? - Physics Stack Exchange

I tried to calculate one of the problems in the textbook Gauge Theory of Elementary Particle Physics by Ta-Pei Cheng and Ling-Fong Li. On page 248 you can find the following calculation of a loop

Quantum Field Theory for the Gifted Amateur: Lancaster, Tom, Blundell, Stephen J.: 9780199699322: : Books

Kitaev's Quantum Double Model from a Local Quantum Physics Point of View

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quantum field theory - What is the missing part of the argument needed to justify the claim of (2.52) in Peskin and Schroeder's QFT textbook? - Physics Stack Exchange

Quantum Field Theory for the Gifted Amateur: Lancaster, Tom, Blundell, Stephen J.: 9780199699322: : Books

quantum field theory - Electron Positron annihilation Feynman Diagram - Physics Stack Exchange

quantum field theory - Scalar QED photon vacuum polarization - Physics Stack Exchange

What is the relationship between Quantum Field Theory and The Standard Model, are the two compatible? - Quora