# There were undefined references [duplicate]

I get this error when I try to run my file. I try to put in a reference, but I only got [?]. This is the main document:

\documentclass[10pt,a4paper]{article}
\usepackage{standalone}
\usepackage[english]{babel}
\begin{document}
\tableofcontents
\newpage % Hieronder voeg je de hoofdstukken in
\input{../tex/hoofdstuk1}
\input{../tex/hoofdstuk2}
\newpage
\section*{References}
\bibliography{bibliography.bib}
\end{document}


And this is the .bib file.

In the file hoofdstuk2 I refer to a source like this: \cite{Tsao2013558} I don't understand why my reference is displayed as [?]. Can someone help me?

## marked as duplicate by Werner, Maarten Dhondt, Jesse, Svend Tveskæg, user13907 May 18 '16 at 18:26

• Welcome to TeX.SX! Rather than posting screenshots it is much better to post the actual code (and then highight it using the {} symbol in the gui). This makes it much easier for people to help you because they can cut-and-paste your code, allowing them to easily edit and test it on their own system. – Andrew May 18 '16 at 10:52
• Did you run pdfLaTeX(F6), then BibTeX (F11) and then pdfLaTeX (F6) twice? – Torbjørn T. May 18 '16 at 10:54
• I did but it is stel not working. – user105939 May 18 '16 at 11:06
• Possible helpful: Question mark instead of citation number – Richard May 18 '16 at 12:28
• If the post Sam linked doesn't help you, I suggest you post also the raw text of your .bib file (at least the relevant part). And also hoofdstuk2.tex. Please don't post it as a comment but edit your question. I did part of that so that you can see how it works. This will increase your chances of getting help – sheß May 18 '16 at 16:47

The problem with the given MWE is that it does not contain a \bibiographystyle thus bibtex stops with the error
I found no \bibstyle command---while reading file hoofdstuk2..aux

and it does not produce a .bbl file.