$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.17
\begin{equation} \begin{gathered}\label{equation:correspondence-infinity-two-strong} \xymatrix@C =50pt@R=50pt{ X_{0,0} \ar [dr]^{u} & & X_{1,1} \ar [dl]_{u'} \ar [dr]^{v} & & X_{2,2} \ar [dl]_{v'} \\ & X_{0,1} & & X_{1,2} & } \end{gathered} \end{equation}