然而，兰皮诺和其他人对传统主义者的一个基本假设提出了质疑：在整个地球历史中，冰川期是周期性发生的。

Yet Rampino and others question one of the traditionalists' basic assumption: the periodic occurrence of glaciation throughout Earth's history.

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但强迫堕胎的丑闻仍周期性发生。

But scandals over forced abortions continue to arise periodically.

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在交通系统中，有许多事件是周期性发生的。

In traffic system, many events are occurred periodically.

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