Are you sure these are all the same? I can't check from here (on my mobile, poor reception) but the URLs look significantly different. This one is a slide deck, one of the ones you quote is a video.
Added in edit:
It does look like this one - http://news.ycombinator.com/item?id=4651882 - really is a duplicate, but it got no votes and no comments, so perhaps a repost is in order.