这里，我们选择使用书籍，而不是作者来作为主题的目的是让主题应用于它下面的整个层次范围。
We have chosen to use the book as the subject, not the author so the subject applies to the hierarchical scope below where we define it.
等号可以完成与赋值箭头 （assignment arrow）相同的功能，但是只能用于最高层次范围，不能用于嵌套的表达式。
The equal sign does the same thing as the assignment arrow, but may only be used at the top-level scope, not also in nested expressions.
我们应该在不同层次、不同范围、通过多种途径推动区域经济一体化。
We should promote regional economic integration at different levels, in various scopes and through multiple channels.
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