I am trying to use Natbib to print et al. for authors, for instance "Jeannet et al. [1]".

\documentclass[runningheads,orivec]{llncs}
\usepackage{natbib}
\begin{document}
\cite{jeannetmine09}    % gives [1]
\citet{jeannetmine09}   % gives (author?) [1]
\citep{jeannetmine09}   % gives [1]
\bibliographystyle{plain}
\bibliography{bibfile}
\end{document}


where bibfile.bib contains

@InProceedings{jeannetmine09,
Author = {Jeannet, B. and Min\'e, A.},
Title = {{APRON}: A Library of Numerical Abstract Domains for Static Analysis},
BookTitle = {Computer Aided Verification, CAV'2009},
Volume = {5643},
Pages = {661--667},
Series = {LNCS},
Year = {2009}
}


I don't know why \citet{jeannetmine09} can't find the authors as this link shows. Could anyone help?

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Use plainnat as bibliography style. –  Marco Daniel Mar 18 '12 at 17:03
plainnat seems to always show the authors... What I want is to show the authors when I need... –  SoftTimur Mar 18 '12 at 17:08
\bibliographystyle{plainnat} and \usepackage[numbers]{natbib} –  egreg Mar 18 '12 at 17:14
Your example bib entry has exactly two authors. However, the author-year citation method FirstAuthor et al is usually applied when there are three or more authors. (The plainnat.bst file follows this practice.) By the way: "et al" (short for "et alii" in this case) literally translates to and others -- note the plural form of "others". When there are exactly two authors, there's normally little gain to be achieved by replacing "and SecondAuthor" with "et al", right? –  Mico Mar 18 '12 at 20:33
The link you provide is to a natbib reference sheet that's more than 10 years old! You may want to consult a somewhat more up-to-date reference piece, such as natbib's own user guide, available at ctan.org/tex-archive/macros/latex/contrib/natbib. –  Mico Mar 18 '12 at 21:10

I answered in the comment you should use the bibliography style plainnat.

In combination with this bibliography style you have to submit the option numbers to natbib.

Here the complete example:

\documentclass{article}
\usepackage[numbers]{natbib}

\usepackage{filecontents}
\begin{filecontents}{bibfile.bib}
@InProceedings{jeannetmine09,
Author = {Jeannet, B. and Min\'e, A.},
Title = {{APRON}: A Library of Numerical Abstract Domains for Static Analysis},
BookTitle = {Computer Aided Verification, CAV'2009},
Volume = {5643},
Pages = {661--667},
Series = {LNCS},
Year = {2009}
}

\end{filecontents}
\begin{document}
\cite{jeannetmine09}    % gives [1]

\citet{jeannetmine09}   % gives (author?) [1]

\citep{jeannetmine09}   % gives [1]

\bibliographystyle{plainnat}
\bibliography{bibfile}
\end{document}


Result:

PS: Please don't provide examples with unknown (i.e. not on CTAN) document classes unless (i) the class is relevant to the problem you're having and (ii) you supply a link to the class.

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Thanks for your answer... Now the question is how to make "et el." italic, instead of "et el."? Do I have to modify the .bst file as some posts suggest? –  SoftTimur Mar 18 '12 at 17:45
@SoftTimur: You have to modify the bst file. –  Marco Daniel Mar 18 '12 at 17:55
@SoftTimur: Or you switch to biblatex –  Marco Daniel Mar 18 '12 at 18:02
Did you mean to suggest the use of the option authoryear, rather than numbers? The numbers option simply instructs natbib to use a numeric citation style when instructions such as \cite and \citep are encountered. –  Mico Mar 18 '12 at 21:12