In good tradition, we'll finish our seasonal program with a quiz, which is prescheduled for December 25th, 4pm Central European Time, that's 10am on the East Coast. This year's prize is a BackRe(action) mug (see photo), though of course it's more about the fun than about the prize.
Every year I put together the questions and use Stefan as a guinea pig. If he manages to solve the quiz in less than 10 minutes it's too easy. If he hasn't worked it out in 2 hours, taking into account that he knows fairly well the likely sources I have used, it's too difficult. On the Stefan-scale, this year's quiz is more difficult than the ones before, so don't miss it!
The quizzes from the previous years are here: 2007, 2008, 2009, 2010.