The sense of mission, without which man won't go that far, is the internal source of motivation.

使命感是动力的内在源泉，没有明确使命感的人走不了太远。

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The traditional moral noumenon in China was a dual one which regarded "God" as an external source and "Heart" as an internal source.

中国传统道德本体是以“天”（天帝）为外倾之源和以“心”（良心）为内倾之源的二元道德本体；

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Of course, the sales force is not the only internal source for key account managers.

当然，销售队伍不是关键客户经理的唯一内部来源。

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Admittedly, this unusual memory requires an internal light source, but the amount of illumination required is tiny and consumes less power than the logic circuits that are used to read data in and out.

ECONOMIST: Just press print

Petroleum caught on early as the main fuel source for internal combustion engines because it was plentiful and cheap to refine.

FORBES: Veggie Oil Smells Better Than Diesel, But It's No Slam Dunk

Last week the FDIC filed suit against Colonial Bank auditor PwC, and internal audit co-source vendor Crowe Horwath, for professional malpractice and breach of contract.

FORBES: A Tale of Two Lawsuits -- PricewaterhouseCoopers and Colonial Bank