$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
9.19
\begin{equation} \begin{gathered}\label{equation:solution-space-fibration} \xymatrix@R =50pt@C=50pt{ A \ar [d]^{f} \ar [r] & X \ar [d]^{g} \\ B \ar [r] \ar@ {-->}[ur] & Y } \end{gathered} \end{equation}