The presentation from the classes held on 9/20-9/21 is now posted on the course specific page. Please review it, including the slide notes which are a recapitulation of the lecture. I don’t always post my narration, but since this one is somewhat complex (and, I think, critical to an understanding of the work), I want to make sure that you have access to the ideas, regardless of the quality of the notes you took in class. The lecture notes follow the presentation itself, so keep scrolling. The notes include reference points so that you can tell which slides correspond with the explanatory text. Let me know if you have any questions.