\begin{overpic}[width=0.49\textwidth]{ref-pl-an}
\put(1,74){\colorbox{white}{(\sublabel{ref-pl-an}) \href{http://dream.misasa.okayama-u.ac.jp/?q=20110422153539-259-882}{ref-pl-an}}}
%%(\subref{ref-pl-an}) \href{ref-pl-an}
\color{red}
\end{overpic}
<?xml version="1.0" encoding="UTF-8"?>
<acquisitions>
</acquisitions>