在过去的五十年中，产生了许多关于如何这样做的理论。
In the last fifty years, there have been a lot of theories generated about how to do this.
还有，莱利·维尔德将这么一个极度善意的人如何在五十年的时间里激进斗争的引人入胜的故事与一系列的回避、妥协、挫败和失败联系在了一起。
Still, Lelyveld relates the more compelling story of how a supremely well-intentioned man struggled, through five decades of activism, with a series of evasions, compromises, setbacks, and defeats.
其宝塔形结构开始于上世纪五十年代，而如何完成其屋顶的难题已经困扰建筑师们一千年了。
The pyramid dates from the 1950s, but architects have puzzled over how to finish the roof for 1, 000 years.
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