finished tour38

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
finished tour39

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
finished tour40

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
fixes operational comment of tour36

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
finished tour41

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>