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%%  An UIT Edition example
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%%  Example 04-18-10 on page 67.
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%%  Copyright (C) 2010 Herbert Voss
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%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
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%%  See http://www.latex-project.org/lppl.txt for details.
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{177.70511pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands

\StopShownPreambleCommands
\begin{document}
\section{Function $f(x)=x^2$}
\begin{description}
\item[This is $y=f(x)$] only a demonstration.
\item[And $z=f(x,y)$] another demonstration.
\end{description}
\end{document}