从1991年3月到1993年3月，第三阶段的重点是对这些活动做精细的改进并且使其制度化。

Phase III, from March 1991 to March 1993, focused on the refinement and institutionalization of these activities.

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第三种类型的山可能是由于火山活动形成的，一般发生在活动性褶皱带地区，如北美西部的喀斯喀特山脉。

A third type of mountain may be formed as a result of volcanic activity which occurs in regions of active fold mountain belts, such as in the Cascade Range of western North America.

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第三，由肌肉活动产生的瞬间的电信号很容易干扰真实的脑电波信号。

Third, electrical signals generated by muscular activity such as blinking are easily confused with actual brain-wave readings.

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