LaTeX: bibliography per chapter

That one is a TeX FAQ item:

A separate bibliography for each “chapter” of a document can be
provided with the package chapterbib (which comes with a bunch of
other good bibliographic things). The package allows you a different
bibliography for each \included file (i.e., despite the package’s
name, the availability of bibliographies is related to the component
source files of the document rather than to the chapters that
logically structure the document).
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