Interesting video below on YouTube with Sam Byrd's swing. A lot of you may not know who Byrd was, but you should. It's been said that Byrd helped get Hogan's swing on track. Byrd was actually a professional baseball player before he was a pro golfer and used to play with Babe Ruth and Lou Gehrig.
While playing ball with Ruth and Gehrig, one of the drills that they used to do was to take a towel and place in under the armpit of their leading arm (left arm for righties, right arm for lefties). Byrd applied this same exact concept to golf and thus "left side connection" (for righties) was applied. Byrd made particular note that as far as Ruth could hit a baseball, he was ironically a short hitter of the golf ball. Why? Because he wasn't "connected" with his lead arm.
This later morphed into the "left side connection" that one of his protege's Jimmy Ballard teaches. Ballard was probably the biggest name teacher in the 80's before Leadbetter came along and is still a guy that teaches a lot of pros like Rocco Mediate and has other pros bounce ideas off of.
I'm actually in part working on "left side connection" as well. Although I look at it as more or less staying connected and at the top of the swing of the I want to feel the connection while I'm rotating the zipper right at the target. This has not only helped me sustain the lag, but also helped me drop the club in the slot on the downswing better as well. I kind of think of it as basically delaying the release of the #4 power accumulator (left arm & left shoulder).
Anyway, according to legend Hogan started using the towel drill and it immediately got rid of his problems with the hook. Here's a look at Byrd's swing in slow motion: