按照数学家们的分类，三叶形是最简单的纽结。 所谓纽结，它是三维空间中不与自己相交的封闭曲线，或者说是三维空间中与圆周同胚的图形。

The trefoil is the simplest knot in mathematicians' classification.

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在德国，红牛发言人坚称，在欧洲和美国，他们公司的产品，同其他含有古柯叶的提取物的产品一样被认为是安全的。

In Germany, the red Bull spokesman insisted that his company's product, along with others containing the coca leaf extract are considered safe in Europe and the U.S..

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000万年前银杏叶的化石同今天找到的几乎没有什么不同。

Fossil ginkgo leaves 270 million years old are little different than the ones found today.

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This is, I think, how we need to understand the various occult symbols in another great poem from this phase in his career, a little bit further on, "The Second Coming," on page 111.

我想这就是，我们去理解叶芝同时期另一首,伟大诗歌中神秘意象的方法，以更深刻地理解它，《第二次降临》在111页。

耶鲁公开课 - 现代诗歌课程节选