# Bibliography sections without duplicate entries

I am creating a document using biblatex. The document needs multiple separate bibliographies, as provided by the refsegment environment. The same work may be cited in multiple refsegments, but I want the citation to only appear in the first bibliography where it is used and not in latter ones. Citations in subsequent segments should point back to this previous bibliography. Is this possible to do automatically using biblatex?

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The segment=<integer> option for \printbibliography limits the bibliography to entries cited only in reference segment <integer>. This filtering is also applied in \bibbysegment.

You can limit printing to newly-cited entries by applying additional filters. This approach was taken in a similar question for numeric styles. Internally biblatex tracks the entries cited in a reference segment using a list of entry keys. So an alternative way is to add only new keys to this list.

The document below gives a demonstration. Note that you need citation tracking enabled for the \ifentryseen test to work.

\documentclass{report}
\usepackage[style=authoryear,citetracker,backref,refsegment=chapter]{biblatex}

\makeatletter
\patchcmd{\blx@citation@entry}
{\ifinlistcs{#1}{blx@segm@\the\c@refsection @\the\c@refsegment}
{}
{\ifboolexpr{ test {\blx@ifentryseen@global{#1}}
or test {\ifinlistcs{#1}{blx@segm@\the\c@refsection @\the\c@refsegment}} }
{}
{}{}
\makeatother

\section*{References for Chapter \ref{refsegment:\therefsegment}}}

\begin{document}
\chapter{First}
\textcite{companion,cms}
\chapter{Second}
\textcite{companion,cms,markey,ctan}
\end{document}


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+1, but you might want to change the subbibliographies headings to "References first cited in Chapter [...]". –  lockstep Jun 2 '12 at 18:23
Perfect, thank you! –  Nick Hawes Jun 3 '12 at 12:20
Assuming one doesn't want to split bibliographies by topic, entry type, and the like, biblatex allows bibliographies for the document as a whole as well as bibliographies by "refsections" or "refsegments". The difference between the latter two is that the labels of refsections are local to the environment while the labels of refsegments are uniqe across the entire document (similar to a consolidated bibliography). But all three bibliography types have in common that an entry cited in a certain document part (entire document/refsection/refsegment) will also be included in the bibliography of the respective part. Your proposed document design deviates from that, and the need for some (but not all) entries cited in a certain part to be looked up in another part's bibliography is, in my opinion, rather detrimental. If your aim is to avoid duplicate bibliography entries at any cost, I suggest a consolidated bibliography for the whole document.