Limit LaTeX natbib author lists

limitnatbib.sty

\newcounter{@maxauthors}
\setcounter{@maxauthors}{3}
\newcounter{@authors}
\def\BibitemOpen{
  \setcounter{@authors}{0}
  \bibitemOpen
}

%\NewDocumentCommand{\@gobbletoend}{u{,\ }}{\fi\fi\showtokens{#1}}
\NewDocumentCommand{\@gobbletoend}{u{,\ }}{\fi\fi}

\newcommand{\bibinfo@X@author}[1]{%
%  \showtokens{#1}
  \ifnum \value{@authors} < \value{@maxauthors}%
    \stepcounter{@authors}%
    #1,%
  \else\ifnum \value{@authors} = \value{@maxauthors}%
    \stepcounter{@authors}%
    \emph{et~al.},\ \@gobbletoend%
  \fi\fi%
  \@ifnextchar,\@gobble\relax
}

First try, doesn't work in all cases