$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
11.18
\begin{equation} \begin{gathered}\label{equation:relative-universality-for-simplex} \xymatrix@R =50pt@C=50pt{ \operatorname{\partial \Delta }^ n \times \operatorname{\mathcal{C}}\ar [r] \ar [d] & \Delta ^ n \times \operatorname{\mathcal{C}}\ar [d]^{H} \\ \operatorname{\mathcal{E}}_0 \ar [r] & \operatorname{\mathcal{E}}} \end{gathered} \end{equation}