[grantsrc]

All are legal. Like someone else said, pay attention to the direction they fall. If they fall forward on their face, it's a pretty good indication that it was in the back.

Another pet peeve, and I heard it on the tape of our game from last week, the location of the head has nothing to do with whether a block was legal or not. As said earlier, it is all about where the contact occurs. All these in this play are at the side.