Citation Undefined: Bib file not recognized

Question

I'm writing a paper for conference and I got stuck: Somehow bib.file is not recognized. The error always saying citation not defined. I don't know how to fix it. Please tell me.

From this template, I coded like this

\documentclass[12pt]{l4dc2023}
\usepackage{times}
\begin{document}
\cite{vonHamburg13}
\bibliographystyle{unsrt}
\bibliography{sample}
\end{document}

and Bib file sample.bib like this

@InProceedings{vonHamburg13,
    title = {Handling Prefixes and Suffixes in Names},
    author = {von Hamburg, Hans and van der Petersburg, Pieter and de Gier, Willhelm and Hirst, Jr, Peter},
    pages = {27-41},
    abstract = {We demonstrate the ability of scripts to parse names containing prefixes such as 'van der' or 'von'. As a further extension, we consider suffices to names such as 'Jr' and 'III'.}
}

Answer 1

The BibTeX run of your example results in the error:

Illegal, another \bibstyle command---line 18 of file mysample.aux
 : \bibstyle
 :          {unsrt}

This is, because class l4dc2023 loads class jmlr and class jmlr already contains

\bibliographystyle{plainnat}

in line 173.

Each \bibliographystyle command writes a \bibstyle command to the aux file. And BibTeX allows only one \bibstyle.

Because of this, command \bibliographystyle can be used only once per document. So you cannot use another bibliography style than the one already selected by the class. More exactly: You cannot use any \bibliographystyle command in your document, because the class already uses one. And because of this, the original sample file l4dc2023-sample.tex from this template does not have a \bibliographystyle command.

After removing the command from your example:

\begin{filecontents*}{\jobname.bib}
@InProceedings{vonHamburg13,
    title = {Handling Prefixes and Suffixes in Names},
    author = {von Hamburg, Hans and van der Petersburg, Pieter and de Gier, Willhelm and Hirst, Jr, Peter},
    pages = {27-41},
    abstract = {We demonstrate the ability of scripts to parse names containing prefixes such as 'van der' or 'von'. As a further extension, we consider suffices to names such as 'Jr' and 'III'.}
}
\end{filecontents*}
\documentclass[12pt]{l4dc2023}
\usepackage{times}
\begin{document}
\cite{vonHamburg13}
\bibliography{\jobname}
\end{document}

There are no more error messages (only some warnings) and the result is:

Note: If you name the shown example tex file cabohahsniceexample.tex, you have to run pdflatex cabohahsniceexample, bibtex cabohahsniceexample, pdflatex cabohahsniceexample, pdflatex cabohahsniceexample to get the shown result. Instead of pdflatex you can use lualatex or xelatex alternatively. If you name the bib file different, you still have to do the same runs, because bibtex has to be run always with the name of the aux-file not the bib-file. So the parameter of the bibtex run is independent from the name of the bib-file. See, e.g., “Question mark or bold citation key instead of citation number” for more information.

Note also: I've used filecontents environment to generate a bib file with a defined file name. So the example will work independent on the file names used, when someone copies the code. However, you always can remove the filecontents environment and edit the bibliography database in any file with extension bib. However in this case, you have also to adapt the argument of the \bibliography command.