Citations aren't working in included file [closed]

Citations I place in included files come up as a '?', yet citations I place in the main file come up correctly. When the same citation is in both, it appears on both.

I am compiling it in the order of pdflatex>bibtex>pdflatex>pdflatex; I think this is the correct order.

I am using Mac OS X lion and MacTeX.

Have I done something wrong?

% main.tex
\documentclass [12pt]{report}
\usepackage {natbib, graphicx}

\begin {document}

\include {introduction}
\include {background}

\bibliographystyle {pjgsm}
\bibliography {bibliography}

\end {document}

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So does introduction.tex and background.tex include their own \bibliography{..} commands? – Werner Jan 11 '12 at 22:27
No, they don't; I tried that with no success. – Will03uk Jan 11 '12 at 22:30
not directly relevant to the question, but do check the page number of the bibliography in the toc; if your bibliography is longer than one page, this page number probably won't be correct. – barbara beeton Jan 11 '12 at 22:58
@barbara beeton - thanks; I'll make sure to fix that – Will03uk Jan 12 '12 at 0:45
I think you spotted the problem by yourself: either use \input instead of \include or try bibtexing each of the included files rather than main... – Xi'an Jan 14 '12 at 20:30