$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.63
\begin{equation} \begin{gathered}\label{equation:covariant-transport-categorical-pullback-square3} \xymatrix@R =50pt@C=50pt{ \mathscr {F}_{00}(D_{00} ) \ar [r] \ar [d] & \mathscr {F}_{01}( D_{01} ) \ar [d] \\ \mathscr {F}_{10}( D_{10} ) \ar [r] & \mathscr {F}_{11}( D_{11} ) } \end{gathered} \end{equation}