%% 
%%  Example 07-07-5 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{158.31393pt}
\setlength\parindent{0pt}
\usepackage[T1]{fontenc}
\usepackage{kpfonts}
%StartShownPreambleCommands
\usepackage{amsmath}
\newsavebox\eqbox
\sbox{\eqbox}{$\null=\null$}
\newcommand\Vdots{\makebox[\wd\eqbox]{\vdots}}
%StopShownPreambleCommands
\begin{document}
\begin{align}
 a_1 & = b_1    & c_1 & = d_1 \\
 a_2 & = b_2    & c_2 & = d_2 \\
 a   & \Vdots b &     & \Vdots \nonumber \\
 a_n & = b_n    & c_n & = d_n
\end{align}
\end{document}
