\documentclass{report}
\usepackage{amssymb, amsmath, hyperref}
\usepackage{preamble}

\begin{document}


\input{./src/cat/index.tex}
\input{./src/topology/index.tex}
\input{./src/fa/index.tex}
\input{./src/measure/index.tex}

\bibliographystyle{abbrv} % We choose the "plain" reference style
\bibliography{refs} % Entries are in the refs.bib file


\end{document}