mbostock/bost.ocks.org — pull request #11 by dandv (2013-05-06 06:29:39+00:00)
Title: Link to "the join" on first use, and note its explanation later

"The join" (and `enter` and `exit`) are key concepts, yet they aren't described yet at this point in the presentation. They are explained three slides later, and that causes the new user to do a double take.