Revert "book 4"

This reverts commit a38b52e94dd291784feacf28759764dda1fae51c.
Revert "book 8"

This reverts commit 70442b95ee51f3cc68cce6ed76186fbf8795ab2b.
Revert "book 10"

This reverts commit de58a7b140a81a7ee248352bf1e172093f0118c6.