The price of freedom is eternal vigilance.
【译文】冰与炭不能长久共存,寒与暑不会同时到来。
战略不是规划的后果,而是相反:它是规划的起点。
You build your life around what you fear, and then you spend your life being afraid.
数学是一门活生生的学科,随着新的思想和发现不断演变。