Chess is a scientific game and its literature ought to be placed on the basis of the strictest truthfulness, which is the foundation of all scientific research. — W. Steinitz

A41-A42

**A41**
1.d4 d6	Modern:
2.Nf3 Bg4	Modern: Tartakower
2.Nf3 Bg4 3.c4 Nd7 4.Qb3 Rb8	Modern: Tartakower (Chigorin)
2.c4 c6	Modern: Anglo-Slav
2.c4 g6 3.Nf3 Bg7 4.e4 Bg4	Modern: Rossilimo

**A42**
1.d4 d6 2.c4 g6 3.Nc3 Bg7 4.e4	Modern: Averbakh
4…f5	Modern: Averbakh (Randspringer)
4…c5 5.Nf3 Qa5	Modern: Averbakh (Pterodactyl)
4…Nc6	Modern: Averbakh (Kotov)