Using non-performing rubber trees as a source of power also helps rejuvenate rubber production by making room for new planting.

VOA: standard.2009.09.13

And so Richard is learning a grammar of race even while he tries to work out how to use language as a source of power in his family.

所以理查在学习语言的艺术,虽局限于种族,就是他在家里受尽磨难时也在学习语言的魔力。

耶鲁公开课 - 1945年后的美国小说课程节选