I have nothing to add to what has been said about the significance of this day, 50 years ago, in U.S. history. Yet on this day I can't imagine myself devoting my blog entry to some other subject, so let's see if I can scare up an unusual angle. Well ... there's a striking fact involving the National Football League. One of the weird facets of the weekend following the murder of President Kennedy was that the NFL proceeded with its full schedule of games. Nothing else went on as normal that weekend, but football did. Sports Illustrated magazine ran this on that subject on the 30th anniversary . Of course, there was nothing normal about that Sunday. Less than an hour before kickoff of the early games., Jack Ruby shot Lee Harvey Oswald. In Pittsburgh, the Bears and the Steelers played to a 17-17 tie. "Before the game you're usually talking about picking up blitzes," says former Pittsburgh running back Dick Hoak. "Instead, we were saying, 'Di...