$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
3.3
\begin{equation} \begin{gathered}\label{equation:build-using-horn} \xymatrix@R =50pt@C=50pt{ \Lambda ^{n}_{i} \ar [r] \ar [d] & \Delta ^ n \ar [d]^{\sigma } \\ Y \ar [r] & X } \end{gathered} \end{equation}