% Use LaTeX, PDF2SVG and Inkscape to generate this SVG image.
% Author: FRR, Smimram, Ika
% Date: 11/04/2014

\documentclass{amsart}
\usepackage[paperwidth=26cm, paperheight=4cm, top=0cm, left=0cm, right=0cm, bottom=0cm]{geometry}
\usepackage{amsmath,amssymb,nopageno}
\usepackage[all]{xy}
\begin{document}
\thispagestyle{empty}
\Huge
\begin{equation*}
\xymatrix@C=5em{
  ((A\otimes B)\otimes C)\otimes D\ar[d]_{\alpha_{A\otimes B,C,D}}\ar[r]^{\alpha_{A,B,C}\otimes {1_D}}
  &(A\otimes(B\otimes C))\otimes D\ar[r]^{\alpha_{A,B\otimes C,D}}
  &A\otimes((B\otimes C)\otimes D)\ar[d]^{{1_A}\otimes\alpha_{B,C,D}}\\
  (A\otimes B)\otimes(C\otimes D)\ar[rr]_{\alpha_{A,B,C\otimes D}}&&A\otimes(B\otimes (C\otimes D))
}
\end{equation*}
\end{document}