$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.49
\begin{equation} \begin{gathered}\label{equation:witness-vs-section2} \xymatrix { T_{S} & T_{ S_0 } \ar [l] \\ T_{ S_1 } \ar [u] & T_{S_{01}} \ar [l] \ar [u] } \end{gathered} \end{equation}