在 LaTeX 中，如何编写段落，其中有些段落有编号，有些没有？例如
1.1 \textit{repeat} Lorem ipsum.
1.2 \textit{Inner product spaces} Lorem ipsum.
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1.3 \textit{Examples} Lorem ipsum.
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1.4 \textbf{Scharz's inequality} Lorem ipsum.
\textit{Proof}. Lorem ipsum
1.5. \textbf{Theorem} Lorem ipsum
\textit{Proof} Lorem ipsum
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1.6 \textit{Norm space} From previous theorem, one can define \textit{norm spaces} as ...