\documentclass{article}
\usepackage{xy}
\xyoption{all}

\newcommand{\C}{\mathcal C}
\newcommand{\D}{\mathcal D}

\begin{document}
\thispagestyle{empty}
\[
\xymatrix{
    (FA\bullet FB)\bullet FC\ar[d]_{\phi_{A,B}\bullet 1}\ar[r]^{\alpha_\D}&FA\bullet(FB\bullet FC)\ar[d]^{1\bullet\phi_{B,C}}\\
    F(A\otimes B)\bullet FC\ar[d]_{\phi_{A\otimes B,C}}&FA\bullet F(B\otimes C)\ar[d]^{\phi_{A,B\otimes C}}\\
    F((A\otimes B)\otimes C)\ar[r]_{F\alpha_\C}&F(A\otimes(B\otimes C))
}
\]
\end{document}

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• 2006-03-24 20:23 Smimram 364×199× (8519 bytes) Coherence law for associativity of lax monoidal functors