没有什么比煤矿工人更美国了。

What you actually pay for something is at least twice the listed price because of the energy， time， money needed to set it up， learn， maintain， repair， and dispose of at the end. Not all prices appear on labels. Actual costs are 2x listed prices.

预测未来的最好方法就是创造它。

数学的快乐来自于为理解而奋斗。