最近看一些latex用户的文章，输入的双引号和单引号都是用输入法中的中文模式键入，并不是LaTeX的正确输入方式。
正确的输入方法如下：
使用键盘的 Tab键上侧的`键连续键入两个``然后输入键盘的两个单引号‘’。单引号输入类似。示例如下：
演示代码：
\documentclass{article}
\setlength
\textwidth{150pt}
\begin{document}
\large
Pumas are
``large, cat-like animals'' which are `found in America'. When
reports came into London Zoo that a wild puma had been spotted
forty-five miles south of London, they were not taken seriously.
However, as the evidence began to accumulate, experts from the Zoo
felt obliged to investigate, for the descriptions given by people
who claimed to have seen the puma were extraordinarily
similar.
\end{document}
[转] http://blog.sina.com.cn/s/blog_5e16f1770100gusb.html