$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.24
\begin{equation} \begin{gathered}\label{equation:all-cocart-inner2} \xymatrix@R =50pt@C=50pt{ F_0( i, i ) \ar [r] \ar [d] & F_0(i-1, i) \ar [d] \\ F_0(i, i+1) \ar [r] & F_0(i-1, i+1) } \end{gathered} \end{equation}