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%%  An UIT Edition example
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%%  Example 04-05-12 on page 42.
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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{375.57637pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\setcounter{equation}{14}
\renewcommand\theequation{4.\arabic{equation}}
\StartShownPreambleCommands
\setlength\arraycolsep{2pt}
\StopShownPreambleCommands
\begin{document}
\begin{equation}
\begin{array}{rcl}
\displaystyle % same sizes
\frac{1}{2}\,\Delta(f_{ij}\,f^{ij}) & = & 2\times\Bigg(\sum\limits_{i<j}\chi_{ij}
    \left(\sigma_{i}-\sigma_{j}\right)^{2}+f^{ij}\nabla_{j}\nabla_{i}
    (\Delta f) \\[8pt]
    & & {}+\nabla_{k}f_{ij}\nabla^{k}f^{ij}+f^{ij}f^{k}
    \left[2\nabla_{i}R_{jk}-\nabla_{k}R_{ij}\right]\Bigg)
\end{array}
\end{equation}
\end{document}