解释：两虎相斗而劣狗趁机得到好处。

If you want to be the best, you have to do things that other people aren't willing to do.

数学的快乐来自于为理解而奋斗。

最好的林业实践是那些不留痕迹但改变一切的做法。

法律规范的有效性不在于它的实效性，而在于它的约束力。