\documentclass{article}

\usepackage{graphicx}

\begin{document}

Hello world, I'm in a subdirectory \cite{DouglasAdams}

\input{chapter1.tex}
\input{chapter2.tex}

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\includegraphics[width=0.5\textwidth]{image.png}
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\bibliographystyle{plain}
\bibliography{bibliography}

\end{document}
