Sample file for testing bibtex bibs.

sample-bibtex.tex

\begin{filecontents}{main.bib}
    @Book{knuth1990,
    author    = {Knuth, Donald E.},
    title     = {The {\TeX}book},
    year      = {1990},
    isbn      = {0-201-13447-0},
    publisher = {Addison\,\textendash\,Wesley},
    }
    
\end{filecontents}


\documentclass{article}
\usepackage{filecontents}
\begin{document}

    \cite{knuth1990}

    \bibliography{main}
    \bibliographystyle{plain}

\end{document}