I was trying to listen to one of the lecture on iTunes. and I was under the impression that the lecturer was referring to some sketch. The suggested or popular lectures on the 'Downloads' page have pdf sketches accompanying audio lectures. Where can I find the pdf sketches for old lectures as it is very difficult for me to form a mental picture of what he is referring and pointing to? I am new here and still trying to familiarize myself with your website. Thank you for your assistance.