C30White4 book lines continue
Classical Variation, Rubinstein Countergambit
King's Gambit Declined1. e4 e5 2. f4 Bc5 3. Nf3 d6 4. c3 f5 5. fxe5
Also known as KGD: Classical Countergambit, King's Gambit Declined, Classical Variation, Rubinstein Countergambit.