Understanding The Queens Gambit Accepted

The QGA is a positionally sound and reliable opening, played by world champions Kasparov, Karpov, Anand and Topalov. The authors consider the Classical System with 3.Nf3 Nf6 4.e3 e6, but they in fact prefer alternative, sharper approaches. Against 3.e4 they recommend 3...Nc6 4.Nf3 Nf6!?, against 3.e3 they choose 3...e5! and against 3.Nf3 their weapon of choice is 3...Nf6 4.e3 Bg4!? Other choices and drawish alternatives are given.