$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
3.53
\begin{equation} \label{equation:mather-second-cube3} \begin{gathered} \xymatrix@R =50pt@C=50pt{ \overline{A} \ar [rr] \ar [dd] \ar [dr] & & \overline{B} \ar [dd] \ar [dr] & \\ & \overline{C} \ar [rr] \ar [dd] & & \overline{D} \ar [dd]^{w} \\ A \times _{D} \overline{D}' \ar [rr] \ar [dr] & & B \times _{D} \overline{D}' \ar [dr] & \\ & C \times _{D} \overline{D}' \ar [rr] & & \overline{D}', } \end{gathered} \end{equation}