This is from my TORFL Level 2 grammar book. It's about some ways to use "ли" in the subordinate sentences. And I believe that this is mostly an literary (non-colloquial) expression. For example, there is a sentence like this.
Мы ждали, не приедешь ли ты вечером.
How do you translate this into English? And I'm not sure whether I have to translate the "не".