Sources and history

References serve different purposes: a textbook explains a calculation, an original paper establishes a result in its historical setting, and a later treatment may state its hypotheses more clearly. This chapter helps you find a source and follow the precise use made of it in QFT.org.

Find a source

The bibliography collects sources used in the Foundations and Symmetry volumes. Search by author, title, identifier, or topic. Each entry gives publication information and an access link; its expandable details identify the examined edition and related Library pages.

For a particular equation or theorem, begin with the references beside that claim on the relevant Library page. A bibliography entry identifies a work, while a claim-adjacent citation identifies the section, equation, or printed pages needed to check the statement. The same book can support several quite different arguments.

Read a foundational paper in context

The historical timeline follows three papers behind two recurring tools: Wick’s contraction method and the Källén–Lehmann spectral representation. It is a short reading sequence, not a complete history of QFT.

Read the modern statement first, then compare the original paper’s notation and hypotheses. For contractions, the natural companion is Wick’s Theorem and Free Gaussian Factorization. For propagation functions, use The Källén–Lehmann Representation. This makes it easier to distinguish a genuine difference of assumptions from a change in terminology or normalization.

Follow the evidence for a claim

When a source is revised, an equation is corrected, or competing results use different assumptions, the relevant comparison belongs beside the claim itself. The Research guide addresses open questions and evidence that can change. For established calculations, this handbook and the Library retain the useful formulas together with their conditions and source locations.