% Created 2014-12-12 ven. 10:42
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\author{Laurent Steffan}
\date{\today}
\title{Possible bug in the \LaTeX{} exporter}
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\begin{document}

\maketitle
\begin{equation*}\label{eq:dummy}
  A$_{\B_{\text{C}}}$ 
\end{equation*}

\begin{equation*}
\label{eq:dummy}
  A_{\B_C} 
\end{equation*}

\begin{equation*}
  A_{\B_C} 
\end{equation*}
% Emacs 24.4.1 (Org mode 8.2.10)
\end{document}