In calculus, it has not been proved whether or not the equivalent substitution theorem can be applied to the limit calculation of power-exp ential factions.

但对于求幂指函数极限，可重使用等价代换定理，微积分学教程中却没有论及。

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With the inclusion of the ort in the Olympic Games, it became obvious that some internationally recognised rules for the three Olympic disciplines were e ential.

随着马术加入到奥运会中，这三项赛事国际认证的规则的基本性变得更为显著。

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