%% 
%%  Example 07-03-1 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
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\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
\usepackage[T1]{fontenc}
%StartShownPreambleCommands

%StopShownPreambleCommands
\begin{document}
\begin{equation}
\addtolength{\arraycolsep}{-3pt}
I(z)=\delta_{0}\left\{
  \begin{array}{lcrcl}
    D+z & \quad & -D & \le z\le & -p\\
    D-\frac{1}{2}\left(p-\frac{z^{2}}{p}\right) & \quad & -p & \le z\le & \phantom{-}p\\
    D-z & \quad & p & \le z\le & \phantom{-}D
  \end{array}\right.
\end{equation}
\end{document}
