At this time of year students and instructors alike are EXHAUSTED! Getting enough sleep just doesn't seem possible. The November 2003 issue of Scientific American has a good article on the how and whys of sleep. And, if you think that you are sleep deprived, the February 2013 issue deals with "astronaut insomnia." They're not exactly in a good location to go out and take a long walk to relax you for sleep.