Lecture 12 (9/25/17)

Lecture 13 (9/27/17)

"Lecture 14" (9/29/17 and 10/9/17). There is more than a lecture's worth of notes here. After the 10/9/17 lecture, I added the material starts on p. 14.2 with "Alternative proof" and goes through p. 14.4. The rest of these notes is what I'd intended to post for 9/29/17.