Karl uses 4 videos to illustrate his points: 1) https://www.youtube.com/watch?v=f7XhrXUoD6U&t=0s 2) Starting at 24:55-27:12, https://www.youtube.com/watch?v=JuEJbSLv0mE&t=0s 3) from 13:10 to 16:28, https://www.youtube.com/watch?v=7OdXBB-6fSs&t=0s 4) https://www.youtube.com/watch?v=PUtll3mNj5U&t=0s