Add blue-eyed-ancestor?
Exercise 14.1.3
Exercise 14.1.4
Exercise 14.1.5
Exercise 14.1.6
Exercise 14.2.1
Exercise 14.2.2
Exercise 14.2.3
Exercise 14.2.4
Exercise 14.2.5 and 14.2.6
Exercise 14.3.2
Exercise 14.3.3 and 14.3.4
Exercise 14.4.2
Exercise 14.4.3
Exercise 14.4.4
Exercise 15.1.2
improve Exercise 15.1.2
Exercise 15.1.3
Exercise 15.1.4
Exercise 15.3.1