独立且引用/交叉引用源文档

Question

如何在文档中引用或交叉引用源文档中的项目standalone？

\documentclass{article}
\usepackage[mode=buildnew]{standalone}

\begin{filecontents}{stdalone.tex}
\documentclass{standalone}
\begin{document}
   This is a test \cite{cref}.
\end{document}
\end{filecontents}

\begin{document}

This is the source file.

This works here: \cite{cref}

But does not work here: \includestandalone{stdalone}
\begin{thebibliography}{10}
   \bibitem{cref}
    A test reference.
\end{thebibliography}
\end{document}