[answer to a letter] 回复的信
我从不把书借出，很难讨回书。
I never lend books ; it 's difficult to get them back .
你拿回书了吗？
Did you get it ?
要达到此目的，有效地控制回书量及掌握最新销售数据是必要的。
To achieve this goal , we should have effective control over the return issue and obtain instant market information .
回书回书回书