Refferences to learn mechanics

[tomes1978]

I'm a new official. I have an understanding of the rules, but as long as I've been around football I have never payed much attention to what the officials watch, etc. A veteran crew was nice enough to let me accompany them to a scrimmage on Friday night. I shadowed each position and they even let me run the position after watching them for a few plays. I learned a lot from that but also realized that I have a lot more to learn. I know I'll get the most learning from working lower level games and youth football, which I'm going to do. But I want to have a better understanding of mechanics before I even start to do those games. Does anyone have any suggestions for books, videos, etc. that are easier to understand than the officiating manual?