When you talk about Dallas Cowboys coach Jason Garrett's offense, you're also talking about Sid Gillman.
ESPN has a wonderful series regarding some of the great coaches in NFL history, and there's a profile on Gillman.
There are numerous coaches who coached or learned under Gillman and others associated with him for years.
Garrett learned his offensive system from Norv Turner, who learned it from Don Coryell, who learned it from Gillman. The NFL coaching life is a hard one, but it's a rewarding one if you win games.
Garrett is trying to do that now, but it all starts with the teachings of Gillman.