If the detention center has a library, you can write to your friend and ask him to borrow it from their discipline. The library there also has all kinds of books-novels, classics, practical, popular science, law ... It doesn't matter.

Ps: Your friend has been in a small prison, so he can't go to the library by himself, so he can only make a phone call.

Their discipline helps to borrow money.

Here, we just got out of it. Don't make me angry.