Revert "book4"

This reverts commit 53443648632a7616e82d78986f23dc1525dd452c.
Revert "book8"

This reverts commit 2ed33b7f8f7f8cd42a0d27272d9acdeb75757e49.
Revert "book10"

This reverts commit 99f60e98d0c25bc23b4b41dcac5456597b082c88.