数学是关于概念之间关系的科学，与这些概念的内容无关。

Leadership is about making the tough calls and standing by them.

解释：第一次击鼓能振作士兵们的勇气，第二次击鼓可以使士兵们的勇气低落，第三次击鼓士兵们的勇气就消失了。

Small-scale fishers and farmers are the unsung heroes of sustainable aquaculture.

Customer loyalty is earned, not bought.

书籍是理解自己和别人的钥匙。