First, review all the information in your mind right before you go to sleep.

首先，在你睡觉之前在你的脑海中复习所有的信息。

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First, there may be a brief cessation or reduction of breathing when falling asleep as the sleeper waxes and wanes between sleep and wakefulness and their differing control mechanisms.

首先，睡眠者在半梦半醒及不同调节机制之间转换时进入睡眠状态，呼吸可能短暂地停止或减少。

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This was during the first deep sleep period, the researchers said.

研究人员说，这发生在第一次深度睡眠期间。

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But here is something that scientists now know: A team led by Professor Fu has reported the first genetic link to how much sleep we need.

VOA: special.2009.08.26

First of all,notice the obvious point that sometimes people die in their sleep,unexpectedly.

首先，有时人是在睡梦中无预兆地死去。

耶鲁公开课 - 死亡课程节选

I've found some people really have to come to the first and second row because they claim that if they don't hear me they cannot really go to sleep.

我发现有些人必须得在第一,二排睡觉,因为他们说如果听不到我的声音,他们就无法入睡

耶鲁公开课 - 基础物理课程节选

"It is my fourth visit to Japan and it is the first timeI sleep well, " Waseige said.

BBC: Belgians shake off injuries

Ekirch found that references to the first and second sleep started to disappear during the late 17th Century.

BBC: The myth of the eight-hour sleep

During the first stint they could sleep up to nine hours per night, and during the other they were restricted to just four hours.

CNN: Sleep deprivation spurs hunger