# Can I use the same label for different entries with multiple bibliographies?

I work on fairly large documents that put together many seperate *.tex files as well as seperate *.bib files made by different people. I am using bibunits package for bibliographies after each project that I include into my document -- I do not have a global bibliography.

Currently, I am trying to solve the following problem: when I have two different *.bib files but they contain the same bibliography-entry with the same abbreviation, my second \cite refers to the first bibunit-bibliography instead of the second one.

How do I prevent bibunits from referring to another bibunit than the one I am citing in?

To clarify:

\documentclass{book}
\usepackage[subsectionbib]{bibunits}
\defaultbibliographystyle{plain}
\begin{document}

\begin{bibunit}
\cite{source} %first citation
\putbib[references1]
\end{bibunit}

%I need a barrier here, because..

\begin{bibunit}
\cite{source} %this second citation uses the numbering from the first bibunit
\putbib[references2] %instead of referring to this bibunit
\end{bibunit}

\end{document}


Now, I know I could just rename the entry in references2. However, it's not possible for me to check every single entry in the approx. 40 *.bib files that are used in the document and I am looking for a permanent solution. I would also prefer not to merge the different *.bib files into one.
Any ideas?