Sorry for the delay in getting David's lectures up and available. Here are the first two. The third does not exist due to technical problems. Or, to be more accurate, it does not exist in this world.
Interestingly, this third lecture cast aspersions on sidewards movement and though it is true that I have a fondness for this operation and would do almost anything to defend its viability and utility, you can rest assured that the absence of this third scurrilous lecture (the one attacking SWM) met technical difficulties for entirely innocent reasons.
Moreover, I am currently trying to recover this lecture. I have asked my team of semantics consultants to locate it for me. They tell me that it does exist in some possible worlds, though whether those worlds are accessible from ours is currently under intense technical investigation. They are hopeful (or some of their counterparts are). If anyone has suggestions of how to access the third lecture in those worlds and make it available in ours, please contact me asap. Until then, here and here are the first two.
Thx to Julia Buffinton for uploading the files and getting me the links.