$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.8
\begin{equation} \begin{gathered}\label{equation:thin-filler-in-Corr2} \xymatrix@R =50pt@C=50pt{ X_{1,1} \ar [r]^-{u} \ar [d]^{v} & X_{1,2} \ar [d] \\ X_{0,1} \ar [r] & X_{0,2} } \end{gathered} \end{equation}