 It is often difficult for White to prove an advantage in symmetrical opening lines . As GM Bent Larsen wrote , <unk> a game that began 1.c4 c5 <unk> b6 , " In symmetrical openings , White has a theoretical advantage , but in many of them it is only theoretical . " GM Andrew Soltis wrote in 2008 that he hates playing against the symmetrical <unk> 's Defense ( 1.e4 e5 2.Nf3 Nf6 ) , and accordingly varies with <unk> , the Vienna Game . However , there too he has been unable to find a way to an advantage after the symmetrical 2 ... Nc6 <unk> g6 <unk> Bg7 , or after <unk> Nf6 ( <unk> to the Four Knights Game ) <unk> <unk> 5 @.@ 0 @-@ 0 0 @-@ 0 <unk> d6 <unk> <unk> <unk> Nd4 <unk> <unk> , or <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> <unk> d5 , when <unk> ? ! e4 ! may even favor Black . 
