我确实需要使用\marginpar类似以下代码：
\documentclass[11pt,a4paper,twoside,openright]{book}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{lipsum}
\begin{document}
Ut purus elit, vestibulum ut, placerat ac, adipiscing vitae, felis.
Curabitur dictum gravida mauris. Nam arcu libero, nonummy eget, consectetuer
id, vulputate a, magna. Donec vehicula augue eu neque.
\begin{minipage}{\linewidth}
\centering
\includegraphics[width=0.5\textwidth]{RedArrow.png}
\captionof{figure}{Ut purus elit, vestibulum ut, placerat ac, adipiscing
vitae\marginpar{Lorem ipsum \ref{fig:RedArrow} dolor sit amet, consectetuer
adipiscing elit.}, felis. Cur- Lorem ipsum dolor sit amet, consectetuer
adipiscing elit.}
\label{fig:RedArrow}
\end{minipage}
\end{document}
但我只是收到错误。我该怎么办？