mem::replace(&mut borrowed.knight, TheDarkKnight).nothing_is_true(); // ok!
```
-You can find more information about borrowing in the rust-book:
-http://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html
+For more information on Rust's ownership system, take a look at the
+[References & Borrowing][references-and-borrowing] section of the Book.
+
+[references-and-borrowing]: https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html