我正在尝试交叉引用定理或定义，但代码不起作用。代码如下。请帮助我。
提前致谢。
\documentclass[justified, twoside]{tufte-book} % Use the tufte-book class which in turn uses the tufte-common class
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%definiting Theorem in tcolorbox
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%definiting Formulla in tcolorbox
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%definiting Remark in tcolorbox
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%definiting Example in tcolorbox
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{1em}% horizontal separation between label and title body
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\begin{document}
\begin{theorem}[Rolle's Theorem]\label{th:rolls}
Let $f:[a, b]\rightarrow \mathbb{R}$ be a function satisfying the following conditions:
\begin{enumerate}
\item $f(x)$ is continuous on the closed interval $[a,b].$
\item $f(x)$ is differentiable on the open interval $(a,b)$.
\item $f(a)=f(b).$\\
Then there exists atleast one number $c$ such that $a<c<b$ and
$f^{\prime}(c)=0.$
In other words $f(x)$ has a critical point in $(a,b)$.
\end{enumerate}
\end{theorem}
\ref{th:rolls}
\begin{example}\label{ex:01}
Verify Rolle's Theorem for $f(x)$, where
\[f\left(x\right)=8 x -x^{2}~~~\text{in}~~[0,8]\]
\end{example}
\ref{ex:01}
\end{document}