v2 of 3rd part Chapter 4: 4.7-4.8
v2 of 3rd part Chapter 4: 4.7-4.8
v2 of 3rd part Chapter 4: 4.7-4.8
v2 of 3rd part Chapter 4: 4.7-4.8
Merge pull request #7 from bjweiner/master

v2 of 3rd part of Chapter 4